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Ricordiamoci  in  grazia,  che  il  cercar 
la  costituzione  del  mondo  e dc’  maggiori 
e de’  pin  nobili  problcmi,  che  sieno  in 
natura. 

Galileo  Galilei. 

Gj.  II.,  Sistemi. 


LAVOISIER. 


EXPERIMENTUM  CRUCIS. 


INTRODUCTION 


TO 


GENERAL  CHEMISTRY. 


A GRADED  COURSE  OF 


ONE  HUNDRED  LECTURES 


BY 


GUSTAVUS  DETLEF  HINRICHS,  M.D.,  LL.D. 


HONORARY  AND  CORRESPONDING  MEMBER  OF  SCIENTIFIC  SOCIETIES  IN  FRANCE, 
GERMANY  AND  THE  UNITED  STATES)  PROFESSOR  OF  CHEMISTRY, 

ST.  LOUIS  COLLEGE  OF  PHARMACY. 


WITH  AX 

ATLAS  OF  EIGHTY 


PLATES, 


REPRESENTING  CHEMISTS,  INSTITUTIONS,  PRIME  MATERIALS, 
CRYSTALS,  DIAGRAMS  AND  APPARATUS)  AND  ILLUSTRATIONS  IN  THE  TEXT. 


ST.  LOUIS,  MO.,  U.  S. 

CARL  GUSTAV  HINRICHS,  PUBLISHER. 

NEW  YORK  AND  LEIPZIG,  LEMCKE  AND  BUECHNER. 
London,  H.  Grevel  & Co.  Paris,  H.  Le  Soudier. 


1897. 


Entered  According  to  Act  of  Congress,  in  the  year  1897.  by 
Gustavus  Hinrichs, 

In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


ALL  RIGHTS  RESERVED  BY  THE  AETHOR. 


PHOTO-ENGRAVINGS  BY  SANDERS  ENGRAVING  CO., 
ST.  LOUIS,  MO. 


PRINTED  BY  R.  P.  STUDLEY  & CO., 
ST.  LOUIS,  MO. 


S'vt>  p , , V 


TO 

Charles  Friedel, 

MEMBER  OF  THE  INSTITUTE  OF  FRANCE, 

PROFESSOR  OF  THE  FACULTY  OF  SCIENCES. 


CONSERVATOR  OF  THE  M I N ER A LOGI C A L MUSEUM 
OF  THE  NATIONAL  SCHOOL  OF  MINES.  OF  PARIS. 


THIS  VOLUME 


IS  DEDICATED  BY 


The  Author 


MONSIEUR  CHARLES  FRIEDEL, 

MEMBRE  DE  L’  INSTITUT, 

Paris,  France. 

My  Dear  Sir  : 

The  Introduction  to  General  Chemistry  here- 
with most  respectfully  dedicated  to  you,  is  intended 
to  give  the  student  a first  view  of  the  broad  field  of 
science  that  has  been  enriched  by  your  researches, 
and  to  serve  as  a supplement  to  existing  treatises 
of  our  science. 

To  you,  the  form  of  a crystal,  the  synthesis  of 
a mineral  and  the  formation  of  a new  series  of 
organic  compounds  have  been  chemical  problems 
of  equal  importance.  Hence  the  solution  of  every 
single  problem  by  your  hands  has  enriched  chem- 
istry with  a new  principle  as  broad  as  the  horizon 
of  your  mind. 

Thus,  when  you  made  the  ancient  dwarfs 
of  the  mountain  speak,  the  crystal  revealed  to  you 
its  true  composition.  Upon  this  you  built  an 
organic  chemistry  of  the  deep,  of  which  that  of 
air  and  sun  is  like  the  spirit. 


Your  official  trusts  have  been  as  broad  as  your 

chemical  work.  The  magnificent  collection  of 
/ 

minerals  at  the  Ecole  des  Mines,  and  Organic 
Chemistry  at  the  Sorbonne,  have  been  equally 
benefitted  by  that  breadth  of  mind  which  the 
specialist  cannot  even  understand. 

I 

Your  recent  establishment  of  Les  Actualites 
Chimiques  makes  all  chemists  of  the  world  your 
debtors.  The  Great  Chemist  of  the  North 
first  sacrificed  his  time  to  such  a task,  eighty  years 
ago.  For  a while,  his  creation  was  continued  in 
another  country,  by  the  kindred  minds  of  a Liebig 
and  a Woehler.  But  with  modern  Byzantinism,  the 
Jahresberichte  have  depreciated  in  character  even 
more  than  they  have  increased  in  bulk.  You 
happily  have  found  a form  in  which  the  thought  of 
Berzelius  arises  to  new  life  for  the  good  of  science. 

That  your  Colleague,  Professor  Schuetzen- 
berger  of  the  College  de  France,  under  your  presi- 
dency, has  delivered  a Lecture  on  work  of  mine  to 
the  chemists  of  Paris,  at  the  Sorbonne,  and  that  you 
have  opened  your  new  Review  with  a full  report 
thereof,  is  acknowledged  as  a great  distinction 
with  gratitude  by 

THF  AUTHOR. 

St.  Louis,  Mo.,  U.  S.,  March  15,  1897. 


A 

^^'Z^'^-r  — e^c^ 


Je  me  suis  propose  d’embrasser,  dans  ma  publication,  la 
science  tout  entiere;  mon  livre  sera  complet,  quand  au  but; 
il  ne  sera  elementaire  que  par  le  choix  des  methodes. 

FRANCOIS  ARAGO, 


Astr.-pop.  T.  I.,  1854, 


PREFACE. 


This  work  embodies  the  experience  of  nearly  forty  years 
behind  the  Lecture  Table.  I have  addressed  fully  ten  thousand 
students  in  the  aggregate. 

For  a century,  our  chemical  text- books  have  been  modelled 
on  one  pattern.  They  all  begin  with  general  principles  that 
require  advanced  knowledge  to  be  understood.  The  student 
is  first  directed  to  observe  that  which  he  cannot  see,  and  to 
comprehend  that  which  it  took  old  chemists  centuries  to  learn. 
At  the  same  time,  that  which  is  common  and  of  great  practical 
importance,  is  withheld  till  late  in  the  course  or  entirely 
omitted.  Many  gases  that  were  of  special  interest  a century 
ago,  are  still  made  prominent,  though  of  no  significance  at 
present,  while  the  instructive  and  useful  gasometric  processes 
are  given  no  place. 

A reformation  seems  necessary.  It  has  been  attempted 
in  this  book.  The  entire  science  is  presented  in  a strictly 
graded  course.  The  principal  points  are  determined  in  the 
order  of  their  historic  growth.  The  discovery  of  oxygen  is 
not  presented  until  its  necessity  can  be  understood ; it  comes 
as  the  dramatic  event  that  it  actually  was  in  history.  The 
atomic  theory  comes  last,  and  is  here  carried  to  completion. 

The  real  authors  of  chemistry  are  the  chemists  that 
created  the  science.  Hence  the  portraits  of  the  makers  pre- 
cede their  work.  The  other  parts  of  the  Atlas  are  equally 
essentfal.  The  pictorial  representation  of  the  prime  materials 
we  would  like  to  have  increased  largely. 


11 


The  present  is  the  Lecture  Course  exclusively.  It  is 
supplemented  by  a Laboratory  Course,  the  guide  for  which  it 
is  our  intention  to  issue  in  another  year.  The  lecture  is  not 
the  place  for  details  on  processes  and  apparatus.  It  is  as 
impossible  to  teach  as  it  is  to  learn  such  details  in  the  lecture 
hall.  At  the  laboratory  stand  such  knowledge  is  acquired 
almost  without  an  effort. 


The  plates  of  apparatus  are  largely  suggestive  of  what  is 
presented  at  each  lecture.  The  experiments  are  sufficiently 
indicated  in  the  text.  Neither  apparatus,  nor  experiment, 
should  ever  be  introduced  simply  for  show  or  amusement. 
They  are  means  to  an  end,  namely  the  establishment  of 
chemical  facts  and  principles. 


This  book  does  not  aim  to  be  a systematic  treatise  on 
compounds.  Of  such  books  there  are  enough.  The  best  by 
far  is  the  Traite  of  Troost,  (11th  edit.,  Paris,  1895);  it  is  a 
masterpiece  of  completeness  and  condensation ; it  gives  a 
maximum  of  chemistry  in  a minimum  of  space. 

The  selection  of  topics,  and  their  order  of  succession,  has 
been  to  me  a matter  of  much  study  and  consideration  for  many 
years.  The  text  has  also  been  most  carefully  written  and 
re-written.  It  has  been  my  constant  aim  to  make  the  text 
concise  and  clear.  Each  lecture  deals  with  a single,  definite 
topic.  It  is  treated  as  a subject  by  itself.  The  best  French 
writers  have  been  my  models  of  style. 


But  the  work  is  before  the  reader  and  the  student, 
respectfully  submit  it  to  their  consideration. 


Si  GCiESTiox:  In  a first  course  it  is  advisable  to  omit  the  more 
difficult  quantitative  inorganic  part  (Lectures  38  to  51)  till  Lecture  80  in 
organic  chemistrv  has  been  heard.  After  that,  and  perhaps  a review, 
the  more  difficult  quantative  parts  can  be  taken  with  greatest  advantage. 


CONTENTS. 


TEXT  OF  ONE  HUNDRED  LECTURES. 

INORGANIC  CHEMISTRY 


I.  Chemic.vl  Agencies: 

I,  Chemistry  and  A1  Kemi.  2,  Weight  and  Measure.  3,  Solids 
and  Fluids.  4,  Fusing  and  Boiling.  3,  Furnace  and  Blowpipe. 

II.  Metals  .\xi)  Minerals: 

6,  Metals,  old  and  new.  7,  Calcination  and  Reduction.  8,  Alloys 
and  Amalgams.  9,  Ores  and  Cleavage.  10,  Crystal  Gems. 
II,  Crystal  Stones.  12,  Rocks  and  Veins.  13,  Salts  and  Spirits. 
14^  Solution  and  Crystallization.  15,  Crystal  Description. 

III.  Chemical  Reactions  : 

16,  Marble  and  Fixed  Air.  17,  Zinc  and  Inflammable  Air.  18, 
Substitution  by  Solution.  19^  Solution  of  Silver  and  Gold.  20^  Re- 
duction in  the  Wet  Way.  21^  Sulphur  and  Sulphides.  22,  Hydrogen 
Sulphide  and  the  Metals.  23,  Iodine  and  Iodides.  24^  Acidimetry 
and  Alkalimetry.  25,  Neutralization  and  Caloration.  26,  Flux  and 
Glass.  27,  Metals  and  Radicals.  28,  Chemical  Reactions. 

IV.  Combustion: 

29,  Combustion  and  Phlogiston.  30^  Combustion  and  Oxygen. 
31,  Oxide  and  Radical.  32^  Analysis  of  the  Air.  33^  Nitrogen, 
Phosphorus  and  Argon. 

V.  Electrolysis  : 

34,  Battery  and  Dynamo.  35,  Qualitative  Electrolysis.  36, 
Applied  Electrolysis.  37,  Equivalent  and  Electricity. 

VI.  Chemical  Formulae: 

38,  Equivalent  and  Volume.  39,  Equivalent  and  Heat.  40,  Atoms 
and  Molecules.  41,  Elements  and  Compounds.  42,  Allotropy  and 
Isomery.  43,  Binaries  and  Ternaries.  44,  Formula  and  Compound. 

\TI.  Chemical  Analysis: 

Quantitative:  45,  Purity  and  Strength.  46,  The  Analytical 

Balance.  47,  Specific  Gravity  Methods.  48,  Analysis  by  Dissocia- 
tion. 49,  Gasometric  Analysis.  50,  Volumetric  Analvsis.  51, 
Gravimetric  Analysis. 

Qualitative:  52,  Spectrum  Analysis.  53,  Dry  Way  Analysis. 
54,  Wet  Way  Analysis  of  Bases.  55,  W'et  Way  Analysis  of  Acids. 
56,  Recognition  of  Specimens. 


13 


ORGANIC  CHEMISTRY. 


VIII.  Organic  Prime  Materials: 

\"egetable:  57,  Organic  Prime  Materials.  58,  Sugar  and  Wine. 
59,  Fats  apd  Oils.  60,  Flower  and  Fragrance.  61,  Indigo  and 
Madder.  62,  Balsam  and  Resin.  63,  Vegetable  Acids.  64,  Vege- 
table Bases.  65,  Neutral  Principles.  66,  Starch  and  briber. 

Animal:  67,  Milk  and  Butter.  68,  Flesh  and  Blood.  69,  Bone 
and  Sinew.  70,  Animal  and  Plant.  71,  Fermentation  and  Life. 

Fossil:  72,  Petroleum  and  Coal.  73,  Gas  and  Tar.  74,  Phenol 
and  Aniline.  75,  Bone  Oil  and  Wood  Spirits. 

IX.  Chemical  Transformations: 

76,  Starch,  Sugar  and  Glucose.  77,  Alcohol  and  Ethers.  78,  Fats 
and  Soaps.  79,  Nitro-Glycerin  and  Gun-Cotton.  80,  Chloracetic 
Acid  and  Chloral. 

X.  Chemical  Constitution: 

81,  Proximate  and  Ultimate  Analysis.  82,  Empirical  and  Molecular 
Formulae.  83,  Radical  and  Structural  Formulae.  84,  Polymeric  and 
Isomeric  Compounds.  85,  Right-  and  Left-Handed  Compounds. 
86,  Tetrahedron  and  Benzol  Ring.  87,  Alcoholic  Compounds. 
88,  Aromatic  Compounds.  89,  Complex  Compounds.  90,  Organic 
Synthesis. 

XI.  Atom-Mechanics  : 

91,  The  Atom  World.  92,  Prismatic  Atoms  and  Boiling.  93,  Atom 
Linkage  and  Fusing.  94,  Atom  Volume.  95,  Isomeric  Atoms. 
96,  Atomic  Rotation.  97,  Atomic  Libr2Ption.  98,  Atomic  Crystals. 
99,  Atomic  Weights.  100,  The  Atomic  Composition  of  the  Elements. 


ERRATA. 

LECT.  24.  Sect.  5:  For  5 cc  read  50  cc;  for  7 in  line  5 read  31; 
Sect.  12,  line  i,  for  proportion  read  preparation.  LECT.  25.  S.  6,  L.3: 
for  ammonia  read  ammonium;  S.  10,  L.  6:  from  calcium,  read  for  cal- 
cium. LECT.  32.  S.  2,  L.  5:  For  hydrometer,  read  hygrometer. 
LECT.  33.  S.  10,  L.  2:  Raleigh,  read  Rayleigh.  LECT.  37.  S.  ii, 
L.  7 : The — ous,  read  the  anomalous.  LECT.  40.  S.7,  L.4:  ForNa27 

read  Na  23.  LECT.  49.  S.  ii,  L.  9:  For  2 Ca  O Cl  = 183,  read 
Ca  (O  Cl)2  = 143;  L.  10,  for  7.629  read  5.96.  LECT.  51.  S.  9,  L.  3: 
Indicated  read  indicator.  LECT.  60.  S.  9,  L.  6:  Add  B 160.  LECT. 
84.  S.  2,  L.  3:  terrible  read  terribly.  LECT.  86.  S.  3,  L.  5,  admir- 
able read  admirably. 


14 


IHE  STUDENTS  ATLAS 


I.  Chemists  and  Institutions; 

Chemists:  17.  In  Old  Kenii. — A Modern  Temple  of  Chemistry 
(Leipzig).  iS,  (hilileo  Galilei.  19,  Lavoisier.  20,  1 luvghens.  21, 
Bovle.  22,  Berzelius.  23,  Liebig.  24,  Bunsen.  25,  Dumas.  26, 
Faraday.  27.  Berthelot.  28,  Ilaidinger.  29.  Padre  Secchi.  30, 
Lemery : \’an  llelmont.  31,  Pasteur;  Volta.  32,  Berthollet;  Dalton. 
33,  Richter:  Stas.  34,  Mitscherlich : Hofmann.  35,  Kirchhoff; 
Kekule.  36,  Claude  Bernard;  Moissan.  37,  Chevreul;  Court  of 
the  Institut. 

Institutions:  38,  Palace  of  the  Institute  of  P'rance;  Ante-room 
of  the  x\cademy  of  Sciences.  39,  Meeting  Room  of  the  Academy; 
The  Institute  of  PTance,  see  pp.  37,  38,  39,  42.  39,  Balance  Room  at 

Breteuil  (International  Bureau  of  Weights  and  Measures).  4O; 
Chemical  Lecture  Halls;  Gratz^  Paris.  41,  Chemical  Laboratories; 
Giessen;  Leipzig.  42,  Chemical  Research  Library:  Secretary 
Berthelot’s  Room  in  the  Palace  of  the  Institute.  43,  A page  from 
the  Saint  Mark  Manuscript. 

H.  Prime  Materials: 

44,  Galileo's  Moons  of  Jupiter:  Meteorite  P'ield  in  Iowa.  45^ 
Amana  Meteorites,  Hinrichs’  Collections.  46,  Gems  (models). 
47,  Veins.  48,  Coal:  Gold.  49,  Vanilla;  Milk.  50,  Sea  Salt:  Rock 
Salt.  51,  Cryolite;  Marble.  52,  Cinchona:  Magnetite. 

HI.  The  Crystal  World: 

53,  Microphotographs  of  Snow  Crystals;  Alexandrite  Crystals, 
Siberia.  54,  Cubical  Crystals,  Rome  de  P Isle.  55,  Calcite  Crystals, 
Hauy.  56,  Beryl;  Corundum.  57,  Hematite.  58,  Magnetite. 
59,  Cuprite:  Garnet.  60,  Zircon.  61,  Topaz.  62,  Topaz;  Alex- 
andrite. 63,  Pyroxene.  64,  Orthoclase;  Anorthite.  65,  Quartz; 
Calcite.  66,  67,  The  Principal  Crystal  P'orms,  according  to  Von 
Kobell.  68,  Blackboard  Sketches  of  Common  Crystals,  and  Student’s 
Goniometer.  69,  Sulphur  Crystals  (with  their  axes). 


IV.  Diagrams  : 

70,  Solubility  in  Water,  Gay-Lussac.  71,  Solubility  in  Water, 
Etard.  72,  Spectra  of  the  Light  Metals,  Bunsen  and  Kirchhoff. 
73,  Chemical  Reactions,  Dry  Way  and  Wet  Way.  74,  Boiling  and 
Fusing  Points  of  Paraffins.  75,  Boiling  Points  of  Acids,  Alcohol, 
etc.,  (log.  a).  76,  Terminal  Substitution,  complex.  77,  Terminal 

Substitution,  simple.  78,  Boiling  Point  of  Isomeric  Ethers.  79, 
Stas’  Determination  of  Silver  Nitrate.  80,  Ilinrichs’  System  of  the 
Elements,  showing  their  Composition. 

V.  Supplement: 

385,  Cleopatra’s  Chrysopoeia,  Berthelot;  Chemical  Valence, 
Ilinrichs’,  1867.  386,  Weight  and  Measure.  387,  Gasometric 

Apparatus.  388,  Gas  Manipulation.  389,  Distilling  and  Extracting 
Apparatus;  Professor’s  Stand,  Chemical  Laboratory,  St.  Louis 
College  of  Pharmacy.  390,  Micrographs  of  Ferments.  391, 
Ilinrichs’  Chemical  Elements,  1867.  392,  The  Dodecahedron;  The 

Pyritohedron.  Hauy,  Origin  of  Secondary  Forms.  393,  Daubree. 
394,  Structure  and  Properties.  The  Paraffins.  395,  Structure  and 
Libration.  Benzol.  396-7.  Ilinrichs’  System  of  the  Elements, 
1867  and  1897.  398,  Origin  of  the  Periodic  Law.”  Atomic 

Weights,  Diamond  Standard.  399^  Half  a page  from  Hinrichs’ 
Programme  der  Atom  Mechanik,  1867.  400,  A Look-Out  to  the 

Old  Pastures  (67,  i). 

Portraits  in  the  Text: 

Agricola.  Daubree.  Lavoisier  in  Prison  under  the  Reign  of 
Terror  (full  page).  Priestly.  Scheele.  Woehler. 


IN  OLD  KEMI. 


THE  STUDENT’S  ATLAS. 

I.  Chemists  and  Institutions. 


A MODERN  TEMPLE  OF  CHEMISTRY 


17 


GALILEO  GALILEI. 


18 


LAVOISIER. 


19 


HUYGHENS. 


20 


BOYLE. 


21 


BERZELIUS. 


LIEBiG. 


BUNSEN 


24 


DUMAS, 


FARADAY. 


BERTHELOT. 


27 


HAIDINGER. 


28 


P.  SECCHI. 


29 


LEMERY. 


VAN  HELMONT. 


30 


PASTEUR, 


VOLTA. 


31 


BERTHOLLET. 


DALTON. 


82 


RICHTER. 


STAS. 


33 


MITSCHERLICH. 


HOFMANN. 

:u 


KIRCHHOFF. 


KEKULE. 

85 


CLAUDE  BERNARD. 


MOISSAN. 

ISOLATING  FLUORINE  IN  THE  SCHOOL  OF  PHARMACY,  PARIS. 


:U) 


COURT  OF  THE  INSTITUTE. 


CHEVREUL, 

AT  THE  AGE  OF  ONE  HUNDRED  YEARS. 


87 


PALACE  OF  THE  INSTITUTE. 


ANTEROOM  OF  THE  ACADEMY. 


38 


MEETING  ROOM  OF  THE  ACADEMY. 


LECTURE  BY  LEMERY,  PARIS,  1680. 
40 


LIEBIG’S  LABORATORY,  GIESSEN. 


IN  KOLBE’S  LABORATORY,  LEIPZIG 


41 


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^ Ci:^H  P dnr  lot, 


^ Bac 


JLcb  p r f p\H  h40  M 


ALCHEMISTIC  SIGNS  OF  THE  METALS. 

SAINT  MARK  MANUSCRIPT.  FROM  BERTHELOT. 


48 


GALILEO  SHOWING  THE  MOONS  OF  JUPITER  TO  THE 
SENATORS  OF  VENICE. 


THE  STUDENT’S  ATLAS. 


THE  GREAT  IOWA  METEOR,  FEBRUARY  12,  1875. 
44 


45 


AMANA  METEORITES.  Hinrichs’  Collections. 


GEMS. 


46 


VEINS,  FREIBERG,  SAXONY. 

ONE-FIFTIETH  NATURAL  SIZE. 


47 


COAL  MINING,  FRANCE. 

EPINAC. 


GOLD  MINING,  TRANSVAAL 

ZULU  MINERS. 


48 


VANILLA. 

JARDIN  DES  PLANTES,  PARIS. 


MILK. 

CENTRAL  PLATEAU,  FRANCE. 


49 


SEA  SALT.  FRANCE. 

BOURG  DE  BATZ,  BRITTANY. 


ROCK  SALT  QUARRY,  SPAIN. 

CORDONNA  VALLEY,  PYRENEES. 

50 


CRYOLITE,  GREENLAND. 

ARKSUT  FJORD. 


MARBLE,  ITALY. 

MONTE  ALTISSIMO. 


51 


CINCHONA,  PERU. 

BARK  GATHERING. 


MAGNETITE  QUARRIES,  ELBA. 

CAPE  CALAMITA- 


r)2 


MICROPHOTOGRAPHS  OF  SNOW  STARS. 


THE  STUDENT’S  ATLAS. 

III.  The  Crystal  World. 


ALEXANDRITE  CRYSTALS.  SIBERIA. 
58 


I.e  CviiEim  lHexaedre  et  ses  Afocii/iaih’oiu 


54 


ROME  DE  LISLE. 


1’aJITIF.  1)E  RAlS(miST>:MKNT 


55 


RENE-JUST  HAUY. 


TAF  Ig 


56 


BERYL.  CORUNDUM. 


57 


HEMATITE.  HEMATITE. 


TAP  XLX 


58 


MAGNETITE,  MAGNETITE, 


59 


CUPRITE,  GARNET, 


TJF  XlVIll 


60 


ZIRCON.  ZIRCON. 


T/IF  XKXMll  (a)  TAF  XXXV/fl  (if 


61 


TOPAZ.  TOPAZ. 


TAF  XXWUl  (f) 


62 


TOPAZ.  ALEXANDRITE. 


63 


PYROXENE.  PYROXENE. 


64 


ORTHOCLASE.  ANORTHITE. 


< 2 3 4 > 6 7 


16  17  IS  <9  20 


< 2 3 4 5 6 


7 8 9 40  H 12  13 


G5 


6G 


67 


CRYSTAL  DESCRIPTION, 


69 


THE  STUDENT’S  ATLAS. 


IV.  Diagrams. 


70 


71 


SPECTRA  OF  THE  LIGHT  METALS. 


0 10  20  30  40  50  60  70  80  90  100  110  120  130  140  150  ICO  170 


blau  violet 

Spcctraltafol  nacli  Kirclihoff  und  Bunsen, 


CHEMICAL  REACTIONS. 


DRY  WAY.  VVET  WAY. 


74 


BOILING  AND  FUSING  POINTS  OF  PARAFFINS. 


BOILING  POINTS  OF  ACIDS,  ALCOHOLS,  Etc, 


76 


TERMINAL  SUBSTITUTION,  COMPLEX. 


uhstitutLOTi  terminale 


( i 


TERMINAL  SUBSTITUTION,  SIMPLE. 


78 


BOILING  POINT  OF  ISOMERIC  ETHERS. 


nitrate  - STas, 


79 


STAS’  DETERMINATION  OF  SILVER  NITRATE. 


80 


1.  CHEMISTRY  AND  AL  KEMI. 


1.  Chemistry  treats  of  the  changes  of  matter.  It  was 
first  practiced  by  the  inhabitants  of  Kern  or  Kemi  (Egypt). 
The  very  name  of  our  science  thus  proclaims  its  ancient  origin. 
Atlas,  p.  17. 

To  understand  this  definition  fully  implies  to  have  studied 
the  SCIENCE  and  practiced  the  ART  of  Chemistry.  Here  it 
must  therefore  suffice  to  explain  the  words  used  in  the  definition. 

2.  MATTER  is  that  which  constitutes  all  things.  We  all 
know  some  metals,  stones  and  ores,  representing  the  inani- 
mate kingdom  of  nature.  Flowers  and  fruits  are  vegetable, 
milk,  blood,  meat  and  bone  are  animal  things.  Chemistry 
deals  with  the  changes  of  matter  from  all  three  kingdoms  of 
nature.  Nor  is  Chemistry  restricted  to  materials  of  this  earth  ; 
the  material  of  the  sun  and  the  stars  has  been  successfully 
investigated  during  the  last  forty  years. 

3.  Motion  and  division  of  matter  are  called  PHYSICAL 
processes ; they  do  not  affect  the  nature  of  the  material  itself. 
The  power  to  produce  such  motion  or  division  may  be  great, 
as  witnessed  on  our  railways  and  in  our  mills.  The  immense 
ball,  thrown  several  miles  from  the  modern  cannon,  does  not 
change  its  material  nature  in  this  act  of  motion;  however,  the 
charge  of  powder  has  disappeared,  it  has  undergone  a chemical 
change. 

4.  But  if  that  ball  be  left  exposed  to  the  air,  the  water  or 
the  earth,  it  will  gradually  be  changed  into  a brownish,  non- 
coherent mass,' which  we  call  rust.  Smaller  and  thinner  iron 
things  are  quite  rapidly  changed  to  rust  throughout.  Objects 
of  copper  turn  green  under  like  conditions.  Gold  remains 
unchanged.  The  change  of  limestone  to  lime  in  the  kiln  is 
also  a radical  one,  practiced  from  time  immemorial  to  make 
mortar.  Such  are  chemical  CHANGES  of  matter. 


82 


LECTURE  1. 


5.  Organic  matter,  that  is  vegetable  and  animal  substance, 
chars  when  heated  while  the  air  is  partly  excluded.  Inflam- 
mable materials  pass  off  during  this  process.  A specially 
offensive  odor  is  noted  when  animal  matters  are  charred. 
Thus  it  is  generally  easy  to  distinguish  mineral,  vegetable  and 
animal  materials  by  a simple  CHEMICAL  TEST. 

6.  All  nature  is  one  boundless  CHEMICAL  LABORATORY, 
and  the  most  skillful  of  all  chemists  are  the  plants  and  animals. 
From  the  same  soil,  water  and  air,  and  by  the  power  of  the 
same  sunbeam,  PLANTS  produce  not  only  their  diverse  materials 
such  as  wood,  leaf,  flower  and  fruit  in  general,  but  each  kind  of 
plant  produces  some  more  valuable  chemical  specialty,  such  as 
the  fragrance  of  the  rose,  differing  from  that  of  the  lily;  the 
potency  of  the  poppy,  differing  from  that  of  the  conium. 
Atlas,  p.  49. 

7.  In  a like  manner,  every  animal  is  a most  wonderful 
CHEMICAL  FACTORY.  The  beginner  should  be  impressed 
with  such  primary  fact  as  the  chemical  change  of  grass  and 
water  into  milk.  Surely,  grass,  water  and  air  are  the  only 
raw  materials  accessible  to  the  cow  in  her  pasture.  And  what 
a remarkable  chemical  product  is  the  milk  produced,  containing 
butter,  cheese,  sugar,  and  mineral  salts  dissolved  and  sus- 
pended in  water!  Atlas,  p.  49. 

8.  Seeing  the  INFINITE  DIVERSITY  of  organic  matter  pro- 
duced from  the  identical  simple  raw  materials  of  soil,  water 
and  air,  we  can  understand  that  profound  thinkers,  twenty 
five  centuries  ago,  considered  all  matter  essentially  one  in  kind. 
For  about  a century  this  idea  has  been  generally  derided  by 
chemists.  It  does  not  seem  to  us  that  the  ancient  sages  were 
greatly  in  error. 

9.  But  if  all  matter  be  essentially  one,  it  seems  possible 
that  any  material  might  be  made  by  art  if  only  sufficient 
knowledge  had  been  acquired.  Hence  ancient  chemists 
(ALCHEMISTS)  endeavored  to  make  gold  from  common  metals, 
and  tried  to  produce  an  elixir  to  give  health  and  prolong  life. 


CHEMISTRY  AND  AL  KEMI. 


8:j 


Working  to  realize  these  high  ideals,  they  laid  the  foundations 
of  CHEMICAL  ART  AND  SCIENCE,  the  two  equally  important 
parts  of  CHEMISTRY.  The  science  we  present  in  the  lecture 
hall,  the  art  we  practice  in  the  laboratory.  Atlas  pp.  40,  41. 

10.  Chemical  science  has  ever  enabled  chemical  art  indi- 
rectly to  make  gold,  and  thus  to  REALIZE  THE  IDEAL  OF 
THE  ALCHEMIST.  Clay  was  converted  into  costly  porcelain; 
coal  tar  was  changed  into  the  colors  of  the  rainbow,  and 
apparently  worthless  ores  are  now  yielding  gold  by  the  million 
dollars  in  Transvaal  and  in  Colorado.  Atlas,  p.  48. 

11.  Chemistry  is  also  approaching  the  second  ideal  of  its 
founders.  The  active  remedial  principles  have  been  extracted 
from  many  plants,  and  even  new  remedies  have  been  pro- 
duced by  direct  synthesis,  the  chemist  imitating  the  work 
done  by  the  living  cell!  Moreover,  practical  hygiene  is  main- 
ly chemical.  Surely,  Chemistry  does  give  health  and  pro- 
long life. 

12.  Until  it  shall  be  deemed  proper  to  deride  Columbus  for 
having  discovered  America  while  he  sought  the  Indies,  we 
will  not  join  those  who  deride  the  early  workers  in  Kemi  for 
having  held  ideals  too  high  to  be  fully  realized  in  three 
thousand  years.  In  Chemistry,  as  everywhere  else,  the 
highest  ideals  are  the  best;  the  distant  star  is  a better  guide 
than  the  near  ignis  fatuus.  Sic  itur  ad  astra. 


Notes.  Deeming  it  essential  to  keep  the  text  as  brief  and  clear  as 
possible,  collateral  and  explanatory  matter,  aiding  in  the  understanding 
of  the  topic  presented,  is  appended  in  the  form  of  short  notes,  precisely 
as  explanations  are  given  at  the  lectures,  but  not  considered  as  part  of 
the  subject  itself,  once  that  being  understood.  The  notes  will  be  prefaced 
by  a numeral  referring  to  the  paragraph  for  which  they  are  intended. 

I.  Chemistry,  in  English,  is  commonly  pronounced  Kem-istry;  sig- 
nifying knowledge  pertaining  to  Kemi.  Chemistry  is  called  Kemi  in 
Danish,  Chemie  in  German  and  Chimie  in  French. 

6.  Among  the  various  plants  represented  in  the  cut  as  growing  in  a 
glass-house  of  the  Jardin  des  Plantes  at  Paris,  the  climbing  Vanilla  will 


84 


LECTURE  2. 


be  noticed,  showing  flower  and  the  valued  fruit,  also  numerous  pendent 
air  roots. 

7.  These  Chemical  factories  (cows)  are  exceedingly  numerous  and 
their  product  aggregates  millions  a year  in  every  country.  When  no 
longer  wanted  for  milk  production,  these  factories  are  let  alone,  and  pro- 
duce meats  and  fats,  hides  and  bones,  all  prime  materials  of  the  highest 
importance.  England  imports  for  40  million  dollars  butter  alone  a year. 

10.  The  new  cyanide  process  with  reduction  by  electrolysis  makes  it 
possible  to  work  low  grade  ores  profitably.  The  Zulus  do  the  mechani- 
cal work  of  drilling,  shown  p.  48;  dynamite  does  the  rest.  The  Trans- 
vaal gold  deposit  is  not  a vein,  but  a stratum,  the  onl}'  stratified  gold 
deposit  in  the  world. 


2.  WEIGHT  AND  MEASURE. 

1.  Any  body  or  thing  occupies  some  definite  amount  of 
space,  called  its  bulk,  measure  or  VOLUME.  It  also  exerts 
some  definite  amount  of  pressure  upon  its  support;  this  pres- 
sure is  called  its  WEIGHT.  Weight  and  measure  are  the  only 
two  general  properties  which  matter  possesses. 

2.  By  adopting  convenient  UNITS,  both  weight  and  volume 
can  be  expressed  by  numbers.  The  standard  units  are  the 
KILOGRAMME  and  the  METER.  Exact  copies  thereof  are 
made  at  the  International  Bureau  of  Weights  and  Measures, 
in  the  Pavilion  Breteuil  at  Saint-Cloud,  in  southwestern  Paris. 
This  Bureau  is  jointly  maintained  by  over  twenty  countries, 
including  the  United  States  and  Great  Britain.  Atlas,  p.  39, 
shows  the  Balance  Hall  of  this  Bureau. 

3.  The  metrical  standards  were  adopted  in  France  a cen- 
tury ago,  to  secure  natural  units  and  uniformity;  even  towns 
having  distinct  units  at  that  time.  The  meter  was  intended 
to  be  the  ten -millionth  partmf  the  earth’s  quadrant  passing 
through  Paris.  The  kilogramme  was  intended  to  be  the  pres- 
sure of  a tenth -meter  cube  of  water  at  its  greatest  density. 

4.  Modern  determinations  have  shown  that  the  quadrant 
really  is  about  10.001.900  meters  and  that  the  kilogramme 
exceeds  the  defined  amount  by  something  less  than  one  ten- 


WEIGHT  AND  MEASURE. 


85 


thousandth  part.  The  actual  material  STANDARDS,  made  a 
century  ago  are,  however,  retained  unchanged  by  the  Interna- 
tional Commission;  the  original  definition  being  sufficiently 
complied  with  for  practical  purposes. 

5.  The  system  of  numeration  in  universal  use  being 
DECIMAL,  the  units  of  weight  and  measure  must  also  be 
divided  and  multiplied  by  tens  to  avoid  useless  reductions. 
The  sub-multiples  are  distinguished  by  Latin  prefixes  (deci, 
centi,  mini),  while  the  multiples  are  designated  by  greek  pre- 
fixes (deka,  hecto,  kilo).  The  mega  is  used  for  very  large 
(million)  and  the  micro  for  equally  small  (millionth)  values. 
Thus  the  micrometer  or  micron  (/^)  being  the  thousandth  of  a 
millimeter,  is  the  usual  unit  for  microscopic  objects. 

6.  THE  BALANCE  is  the  instrument  for  weighing.  It  con- 
sists of  a light,  rigid  beam,  resting  by  means  of  a transverse 
edge  on  a hard  smooth  plane.  Two  smaller  edges  at  the  ends 
of  the  beam  support  like  planes  to  which  the  pans  are  attached. 
The  distances  from  the  outer  to  the  central  edge  (the  arms) 
must  be  equal. 

In  good  (prescription)  balances,  edges  and  planes  are  of 
hardened  steel ; in  the  analytical  balance,  the  planes  are  of 
agate  ; in  the  best  balances,  the  edges  are  also  made  of  agate. 

7.  Weights  are  made  in  sets,  containing  one  5,  one  2 
and  two  1 for  each  digit,  except  the  last,  for  which  commonly 
two  2 and  one  1 are  given  to  complete  the  10  and  allow  a check. 
f;rom  one  gramme  up,  the  weights  are  usually  turned  brass; 
for  subdivisions  of  the  gramme,  platinum  foil  is  used.  Each 
single  weight  is  fitted  to  its  special  place  in  the  box  holding 
the  set.  Chemical  weights  must  be  handled  by  forceps  only, 
never  touched  with  the  fingers. 

8.  In  WEIGHING,  the  body  is  placed  on  the  left  pan,  and 
weights'  are  applied  in  the  order  of  their  magnitude  on  the 
right  pan.  By  a simple  mechanism,  the  beam  is  brought  into 
action  only  for  an  instant  to  see  whether  the  weights  on  the 
pan  are  too  heavy  or  insufficient.  Below  the  centigramme. 


LECTURE  2. 


the  beam  is  permitted  to  oscillate,  the  balance  case  being 
closed  to  prevent  air  currents.  If  the  oscillations  of  the  pointer 
are  equal  on  both  sides,  the  weighing  is  completed. 

9.  Balances  and  weights  obtained  from  reputable  makers 
will  stand  all  TESTS  warranted  by  the  price  paid.  All  details 
about  these  matters  belong  to  the  course  in  practical  chemistry. 

The  balance  being  the  most  sensitive  and  accurate  instru- 
ment of  all,  the  chemist  checks  his  volume  measures  by 
weighing  them  empty  and  filled  with  water  up  to  mark.  Every 
cubic  centimeter  (cc)  should  correspond  to  a gramme  (gr.) 

10.  For  the  ready  measurement  of  volumes  the  chemist 
uses  sets  of  glass  vessels  accurately  graduated  (BURETTES 
and  CYLINDERS)  or  provided  with  a mark  filled  up  to  which 
they  hold  a definite  amount  (FLASKS  and  PIPETTES). 
Graduated  cylinders  with  ground  glass  stoppers  are  also  called 
MIXING  JARS.  The  burettes  are  either  provided  with  a rubber 
tube  and  spring  clamp  (Mohr’s),  or  with  a perforated  ground 
glass  stopper  (Geissler’s)  for  use  with  corrosive  liquids. 

11.  Common  experience  shows  that  bodies  differ  greatly  in 
density;  lead  is  heavy,  chalk  is  light,  cork  even  lighter  than 
water. 

The  SPECIFIC  GRAVITY  (G)  of  a substance  is  the  weight, 
in  grammes,  of  one  cubic  centimeter  thereof.  The  specific 
gravity,  carefully  determined,  is  an  important  characteristic  of 
matter,  enabling  us  to  distinguish  otherwise  similar  bodies. 
Thus  one  cc  of  lead  weighs  11.35  gr. ; or  lead  is  character- 
ized by  its  G being  11.35. 

12.  To  determine  the  specific  gravity  of  any  body,  ascer- 
tain its  weight  (w)  in  grammes  and  measure  its  volume  (v) 
in  cubic  centimeters;  dividing  the  volume  into  the  weight,  we 
evidently  obtain  the  weight  of  one  cubic  centimeter,  that  is 
the  value  of  G.  This  process  applies  to  all  bodies;  the  special 
methods  of  measuring  vary  with  the  nature  of  the  body.  A 
ten  gramme  flask  holds  7.91  gr.  of  absolute  alcohol;  hence 
G is  0.794  for  this  liquid. 


3.  SOLIDS  AND  FLUIDS. 


1.  Matter  presents  itself  in  three  distinct  forms,  namely  as 
solid,  liquid  and  gas.  These  forms  are  also  called  the  three 
STATES  OF  AGGREGATION.  Ice,  wood,  iron,  copper,  are 
solids;  water,  oil,  alcohol,  are  liquids.  The  most  common  gas 
is  atmospheric  air. 

2.  Hold  any  SOLID  body  in  varying  positions,  especially 
in  reference  to  the  vertical,  and  no  change  in  either  shape 
(form)  or  bulk  (volume)  of  the  solid  will  be  noticed.  That  is, 
solid  bodies  possess  a form  and  volume  of  their  own.  In  other 
words,  the  volume  and  form  of  a solid  are  fixed  (constant) 
quantities. 

3.  A LIQUID  contained  in  any  glass  vessel,  handled  in  the 
same  way,  will  exhibit  in  all  positions  a free  surface  which  is 
plain  and  level,  otherwise  it  will  conform  to  the  shape  of  the 
containing  vessel.  If  the  volume  of  the  liquid  is  measured  at 
the  beginning  and  at  the  close  of  such  experiment,  it  will  be  ^ 
found  to  have  remained  unchanged.  Thus  liquids  have  a fixed 
volume,  but  no  form  of  their  own. 

4.  The  FREE  SURFACE  of  the  liquid  shows  near  the  walls 
of  the  containing  vessel  a curved  surface ; concave  for  water, 
convex  for  mercury  in  glass  vessels.  If  a tube  be  inserted, 
the  liquid  will  rise  or  sink  so  much  the  more  as  the  tube  is 
more  narrow  or  hair  like  (capillary).  Hence  the  cause  of  this 
deviation  from  the  plane  surface  is  called  CAPILLARITY. 

5.  Only  vessels  sufficiently  wide  will  show  the  true  plane 
and  level  free  surface  of  the  liquid.  To  FILL  TO  MARK  or 
read  the  volume  on  a graduation,  the  eye  should  be  brought 
exactly  in  the  height  of  this  surface.  If  the  vessel  be  too 
narrow,  the  lower  (for  mercury  the  upper)  curved  surface 
should  be  tangent  to  the  mark  of  capacity  or  graduation. 

6.  The  free  surface  of  the  same  liquid  contained  in  two 
VESSELS,  COMMUNICATING  by  means  of  a sufficiently  wide 
tube,  stand  always  in  the  same  level,  however  the  position  of 


LECTURE  3. 


the  vessels  may  be  changed.  This  is  readily  seen  by  using 
the  burette  with  reservoir,  or  our  gas  burette  open,  and  with 
any  liquid,  including  mercury. 

7.  If  the  exit  tube  of  the  gas  burette  be  closed,  the  free 
surface  of  the  liquid  in  the  burette  and  reservoir  will  no  longer 
be  in  the  same  level;  it  will  stand  low  in  the  burette  if  the 
reservoir  is  raised,  and  vice  versa.  Consequently  the  AIR  in 
the  burette  resists  the  pressure  of  the  liquid  in  the  reservoir, 
and  expands  when  the  reservoir  is  lowered ; it  is  a substance 
or  body. 

8.  Thus  the  air  in  the  closed  gas  burette  has  neither 
volume  nor  form  of  its  own ; its  form  is  that  of  the  containing 
vessel,  and  its  volume  is  dependent  on  the  pressure  to  which 
it  is  subjected.  Such  a body  is  called  a GAS. 

Liquids  and  gases  flowing  freely  from  one  vessel  to  another, 
are  also  designated  by  one  term  FLUID.  A liquid  is  a fluid  of 
fixed  volume;  a gas  is  a fluid  of  variable  volume. 

9.  A gas  may  be  handled  almost  as  readily  as  a liquid,  by 
means  of  the  pneumatic  trough,  flasks  and  cylinders.  The 
PNEUMATIC  TROUGH  is  simply  a wide  vessel  containing  a 
liquid  (water,  mercury)  in  which  cylinders,  flasks,  etc.,  can 
be  filled  with  the  liquid  and  inverted;  they  will  remain 
filled,  and  receive  and  retain  gas  from  any  other  vessel  or 
delivery  tube.  A few  experiments  make  this  familiar.  See 
also  plate  of  gas  apparatus. 

10.  A gas  burette  filled  with  mercury  and  provided  with  a 
stop -cock  at  the  top  can  be  used  as  BAROMETER  and  as  a 
mercurial  air  pump. 

By  raising  the  reservoir,  fill  the  burette  to  a little  above  the 
stop -cock,  then  shut  this.  Now  lower  the  reservoir.  The 
burette  will  remain  filled  with  mercury  so  long  as  the  surface 
of  the  mercury  is  not  more  than  76  cm  lower  than  the  stop- 
cock. If  lowered  more,  the  VACUUM  will  appear  in  the 
burette,  and  the  column  of  mercury  will  remain  invariably  76 
cm.  This  corresponds  to  Torricelli’s  experiment  (1642). 


SOLIDS  AND  FLUIDS. 


89 


11.  To  use  the  burette  as  mercury  AIR  PUMP,  its  stop-cock 
must  be  perforated  lengthwise  and  connected  with  the  receiver 
to  be  exhausted.  By  a simple  turn  of  the  stop-cock,  the 
burette  can  now  be  closed  (A),  or  communicate  with  the  air 
(B)  or  with  the  receiver  (C).  In  position  (B),  fill  the  burette 
with  mercury,  by  raising  the  reservoir;  then  close  (A)  and 
lower  reservoir  76  cm;  now.  connect  with  receiver  (C)  ; then 
turn  to  B,  raise  reservoir  and  drive  out  air.  Continue  these 
operations,  and  the  air  in  the  receiver  will  rapidly  be  reduced 
in  amount. 

12.  If  the  burette  be  equal  to  the  capacity  of  the  receiver, 
the  amount  of  air  withdrawn  at  each  complete  motion  is  one 
half,  leakages  neglected.  Ten  motions  would  reduce  it  to  the 
thousandth  part  of  the  original. 

If  a U tube  with  perforated  stoppers  and  a capacity  of  from 
50  to  100  cc  be  exhausted,  it  will  show  a loss  in  weight  of 
over  one  milligram  per  cubic  centimeter.  This  evidently  is 
(approximately)  the  WEIGHT  OF  THE  AIR. 


Notes  3.  Before  filling  the  vessel,  film  it.  that  is,  move  a small 
amount  of  the  liquid  around  in  the  vessel  so  as  to  cover  the  inside  with  a 
film  of  that  liquid;  then  let  run  and  drip  out  all  that  will  flow.  If  the 
vessel  was  not  filmed,  the  volume  of  the  liquid  used  in  the  experiment 
would  apparently  have  diminished  slightly. 


4.  FUSING  AND  BOILING. 

1.  Solid  ICE  brought  into  a warm  room  melts  or  fuses, 
being  converted  into  liquid  WATER.  The  latter,  heated  in  a 
flask,  soon  begins  to  boil;  while  condensed  vapor  (liquid  drops) 
issue  at  the  top,  the  flask  above  the  water  looks  as  if  it  con- 
tained air,  that  is  the  true  STEAM,  water  in  the  gaseous  state. 

Solid' IODINE  is  also  readily  melted  and  converted  into 
beautiful  violet  vapor.  The  corresponding  experiment  with 
SULPHUR  requires  care,  the  vapors  burning  with  explosive 
violence. 


90 


LECTURE  4. 


2.  In  general,  a fusible  solid,  upon  heating,  will  melt,  and 
a volatile  liquid  will  boil.  By  decreasing  the  heat,  the  vapor 
will  again  liquefy  (condense),  and  the  liquid  will  solidify 
(frequently  crystallize).  Thus  the  state  of  aggregation  of  a 
substance  depends  not  only  on  the  nature  of  that  substance, 
but  essentially  also  on  the  temperature  to  which  the  substance 
is  exposed. 

3.  Heat  does  not  change  gases,  except  in  bulk.  Grasp  the 
receiver  of  our  gas  burette  firmly  with  the  hand,  and  the 
motion  of  the  liquid  will  show. that  the  air  EXPANDED.  With- 
drawing the  hand,  the  air  returns  to  exactly  its  original  volume. 
This  apparatus  accordingly  is  a sensitive  AIR  THERMOMETER. 
With  porcelain  and  platinum  receivers,  it  permits  the  determi- 
nation of  very  high  and  also  very  low  degrees  of  heat.  Com- 
mon thermometers  contain  mercury  or  alcohol. 

4.  Inserting  the  bulb  of  such  a thermometer  into  crushed 
ice,  the  thermometer  will  first  fall  rapidly,  then  more  gradually, 
and  finally  remain  perfectly  stationary  or  fixed,  so  long  as  a 
reasonably  large  amount  of  ice  remains.  This  FIXED  POINT 
of  temperature  at  which  ice  melts  is  called  the  freezing  point, 
and  marked  zero.  In  the  same  manner,  boiling  of  water  is 
found  to  take  place  at  a fixed  point,  called  the  boiling  point, 
which  is  marked  100. 

5.  The  interval  (volume  in  burette  or  in  thermometer  tube) 
is  divided  into  100  equal  parts,  called  DEGREES  of  tempera- 
ture. For  air  thermometers  this  division  is  continued 
indefinitely  upwards  and  downwards. 

6.  If  the  reservoir  be  a 100  cc  pipette  melted  off  at  the 
mark,  and  connected  by  narrow  tube  with  (mercury)  gas 
burette,  and  the  reading  of  the  burette  be  taken  while  the 
reservoir  (bulb)  is  packed  in  melting  ice  and  also  when  sur- 
rounded by  steam  of  boiling  water,  the  EXPANSION  will  be 
found  equal  to  36  cc.  Accordingly  it  is  0.36  cc  per  degree  for 
100  cc.  Gay-Lussac. 


FUSING  AND  BOILING. 


91 


7.  In  the  same  manner,  the  FUSING  POINT  (F)  of  any 
solid  is  that  fixed  degree  of  temperature  at  which  the  solid 
changes  to  a liquid;  so  long  as  any  notable  amount  of  solid  is 
left,  the  thermometer  will  remain  stationary.  If  the  crucible 
with  the  molten  mass  is  set  aside  to  cool,  the  crust  broken 
and  the  remaining  liquid  poured  out,  the  wall  will  often  be 
found  studded  with  beautiful  crystals.  Examples:  Sulphur; 
Bismuth. 

8.  When  heating  a volatile  liquid  in  a flask  provided  with  a 
thermometer,  the  temperature  will  first  rapidly  rise,  then 
gradually  become  stationary,  when  the  liquid  will  begin  to 
boil,  forming  bubbles  of  gas  throughout  its  mass.  This  fixed 
temperature  is  the  BOILING  POINT  (B)  of  the  liquid.  When 
the  vapors  of  the  liquid  are  inflammable,  the  flask  must  be 
connected  with  a condenser.  EVAPORATION  is  the  forma- 
tion of  vapor  at  the  surface  of  the  liquid  only. 

9.  A CONDENSER  consists  of  an  inner  tube  through  which 
the  vapors  pass  from  the  bulb  or  flask  to  the  receiver,  sur- 
rounded by  an  outer  tube  through  which  a current  of  cold  water 
is  kept  flowing  in  the  opposite  direction  of  the  flow  of  the 
vapors.  Accordingly,'  the  chance  of  their  condensation  in- 
creases as  they  pass  on.  The  Liebig  condenser  is  the  most 
common  form  in  use.  Atlas,  p.  23. 

10.  This  entire  process,  comprising  the  change  of  liquid 
into  vapor,  followed  by  the  condensation  of  the  vapor  to  a 
liquid,  is  called  DISTILLATION.  All  non-volatile  matters  will 
remain  in  the  flask;  hence  distillation  enables  the  chemist  to 
separate  the  volatile  from  the  non-volatile  matters. 

If  the  vapors  condense  to  a solid,  the  operation  is  called 
SUBLIMATION.  Example:  Iodine. 

If  the  thermometer  remains  stationary,  it  marks  the  boiling 
point  (B)  of  the  pure  liquid.  If  the  thermometer  is  not  sta- 
tionary, the  substance  is  a mixture. 

11.  In  such  cases,  the  process  of  FRACTIONAL  DISTILLA- 
TION will  separate  these  different  substances  and  yield  nearly 


92 


LECTURE  5. 


pure  materials.  The  portions  or  fractions  of  the  distillate,  pas- 
sing over  between  definite  degrees  of  temperature,  are  kept 
separately;  these  fractions  are  again  run  through  the  distilling 
apparatus  in  succession,  always  removing  the  new  fractions 
when  the  same  limits  of  temperature  are  obtained.  After  four 
or  more  such  runs,  the  fractions  often  pass  over  without  change 
in  temperature,  and  thus  represent  single  substances. 

12.  These  two  fixed  points  F and  B are  most  CHARAC- 
TERISTIC numbers  for  a given  substance,  often  readily  distin- 
guishing otherwise  closely  resembling  materials;  hence  they 
form,  together  with  G,  the  most  important  part  of  the  scien- 
tific description  of  a given  substance.  If  the  material  has  no 
such  fixed  points,  it  is  thereby  proved  to  be  impure,  and 
should  be  subjected  to  fractioning,  to  separate  it  into  its  prin- 
cipal ingredients. 


5.  FURNACE  AND  BLOWPIPE. 

1.  HEAT  not  only  produces  the 'physical  changes  of  volume 
and  state  of  aggregation,  but  it  also  is  one  of  the  common 
causes  of  CHEMICAL  CHANGES.  Inversely,  the  latter  often 
produce  heat.  This  is  especially  the  case  in  the  general  pro- 
cess of  COMBUSTION,  a chemical  action  of  combustible  and 
air.  When  either  combustible  or  air  is  withdrawn,  com- 
bustion ceases. 

2.  WOOD  is  the  oldest  combustible  used;  it  produces  first 
a flame  or  blaze,  and  when  the  volatile  combustible  material 
is  burnt,  the  intensely  glowing  coals  remain.  Such  a fire  is 
too  unsteady  for  most  chemical  purposes.  Hence,  wood  first 
is  charred,  by  slowly  burning  with  limited  supply  of  air,  and 
the  resulting  CHARCOAL  is  used.  It  was  the  only  com- 
bustible of  the  early  chemists. 

3.  In  modern  days,  combustible  liquids  and  gases  have 
come  into  general  use  in  laboratories.  In  the  days  of  Berzelius, 
ALCOHOL  was  used,  especially  in  the  excellent  lamp  with 


FURNACE  AND  BLOWPIPE. 


93 


double  draft,  constructed  by  him.  For  many  years,  illumi- 
nating gas — the  volatile  part  of  bituminous  coal— has  been 
accessible  nearly  everywhere;  it  is  the  best  combustible  for 
most  laboratory  purposes.  Where  gas  cannot  be  had,  gaso- 
line is  frequently  used.  Atlas,  p.  22. 

4.  An  ordinary  gas  flame  is  brightly  luminous,  but  not  very 
hot;  a cool  vessel  held  over  it  will  be  soiled  with  soot.  For 
heating  purposes,  a gas  flame  evidently  needs  a more  abundant 
supply  of  air.  In  the  BUNSEN  BURNER,  this  object  is  per- 
fectly attained,  by  surrounding  the  small  gas  jet  with  a wide 
air  tube  or  chimney,  open  below.  Such  a burner  gives  a tall, 
steady,  almost  invisible  flame,  very  hot  and  depositing  no  soot. 
Glass  tubes  are  bent  and  drawn  easily  in  this  flame.  Atlas, 
p.  24. 


5.  The  Bunsen  Burner  is  used  in  all  laboratories  the  world 
over,  singly  for  ordinary  work,  grouped  into  FURNACES  for 
heating  larger  forms  of  apparatus,  such  as  tubes  and  crucibles. 
These  furnaces  are  provided  with  fire  clay  slabs,  disks,  wide 
tubes,  to  support  or  encase  the  vessel,  so  that  the  heat 
may  be  concentrated  upon  the  vessel  and  not  dissipated  to  the 
surroundings.  Example:  The  so-called  combustion  furnace 
for  elementary  analysis 

6.  The  highest  degree  of  heat  can  only  be  obtained  by 
burning  a large  amount  of  gas  completely  by  means  of  a 
correspondingly  large  supply  of  air.  Accordingly,  the  gas  tap 

must  be  large,  and  the  air 
must  be  forced  by  a bellows 
into  the  center  of  the  flame. 
Glass  is  readily  fused  in 

Glassbiowers  in  ancient  Egypt  SUCh  SL  BLAST  FLAME,  and 

platinum  crucibles  are  brought  to  white  heat  almost  instantly. 
Forms  of  blast  and  blast  furnaces  are  very  numerous,  many 
makes  being  most  excellent. 

7.  By  means  of  the  chemical  BLOWPIPE,  all  the  effects  of 
furnaces  may  be  obtained  on  a small  scale;  it  is  truly  a 


94 


LECTURE  5. 


miniature  furnace.  After  a little  careful  practice,  an  intensely 
hot  flame  may  be  maintained  steadily  and  on  a minute  sample 
produce  almost  instantly  the  varied  effects  of  furnaces.  The 
chemical  blowpipe  was  pefected  by  Swedish  chemists  of  last 
century  and  became  universal  through  BERZELIUS.  Atlas, 
P..22. 


8.  The  main  difficulty  in  using  the  blowpipe  consists  in 
keeping  up  a steady  flame  independent  of  the  regular  work  of 
the  lungs.  TO  INHALE  AND  BLOW  at  the  same  time  seems 
impossible;  but  it  is  quite  easily  done,  if  the  respiratory  out- 
let be  rigidly  limited  to  the  nose  (which  was  specially  made 
for  that)  while  the  cheeks  fully  distended,  by  their  elasticity 
keep  up  the  flow  of  the  small  amount  of  air  required  for 
the  blowpipe. 

9.  Where  much  blowpipe  work  is  to  be  done,  the  inner 
tube  of  a so-called  COMPOUND  BLOWPIPE  may  be  connected 
with  foot  bellows,  while  the  outer  tube  is  connected  with  the 
gas  tap.  With  such  an  apparatus,  blowpipe  work  may  be 
exhibited  to  a class  during  lectures. 

10.  In  every  good  blowpipe  flame  THREE  REGIONS  are  dis- 
tinguished. At  the  luminous,  bluish  point  the  heat  is  greatest; 
it  is  the  FUSING  POINT  (borax  beads,  flame  colorations). 
Beyond  that  point  is  the  OUTER  FLAME,  assisting  combus- 
tion and  producing  calcination  of  metals;  within  is  the  INNER 
FLAME,  in  which  the  calx  may  be  reduced  again  to  the  metallic 
state.  Example:  Lead,  supported  on  charcoal ; flame  colora- 
tions of  nitre  or  salt;  borax  beads  with  copper  or  cobalt  calx. 

11.  As  SUPPORT  for  substances  while  being  heated,  glass, 
porcelain,  platinum  and  carbon,  are  most  generally  used  for 
experimental  purposes.  Fireclay  and  bone  ash  are  also  em- 
ployed. 

The  best  chemical  glass  is  the  so-called  Bohemian  glass, 
which  is  light,  hard  and  difficultly  fusible;  when  heated  in  a 
Bunsen  flame,  it  is  not  quick  to  color  it,  and  first  tinges  it 
purple  only.  Tubes  of  such  glass  are  most  useful. 


METALS,  OLD  AND  NEW. 


95 


12.  Porcelain  in  the  form  of  dishes,  crucibles  and  tubes, 
will  stand  a higher  heat  than  glass.  Platinum  vessels  and 
carbon  (charcoal  and  graphite)  are  used  at  the  highest 
temperatures. 

For  blowpipe  work,  hard  glass  tubing,  platinum  wire  and 
foil,  and  good  charcoal  are  all  that  is  required.  The  properties 
recognized  by  blowpipe  work  are  commonly  called  PYRO- 
GNOSTIC  PROPERTIES  (Berzelius). 


Note. — In  this  lecture,  as  in  all  others,  the  objects  referred  to  are 
abundantly  exhibited,  and  the  operations  mentioned,  are  pi'oduced 
before  the  class.  Thus  work  on  glass  (especially  tubing)  and  metals  v 
is  exhibited;  flame  colorations  and  beads  are  shown.  The  manganese 
bead  is  amethyst  in  the  outer,  colorless  in  the  inner  flame. 


6.  METALS,  OLD  AND  NEW. 

1.  Two  substances  have  attracted  the  attention  of  man  in 
the  earliest  times,  and  continue  to  busy  his  thoughts  to-day. 
The  one  is  and  ever  has  been  most  precious  to  him,  so  that 
he  is  willing  to  accept  a small  portion  thereof  as  reward  for  his 
labors.  The  other  first  was  his  heaven-sent  weapon,  has 
become  the  tool  of  his  hand  and  mind;  he  even  endeavors 
with  it  to  build  higher  than  Babel. 

2.  GOLD  is  the  one  of  these  bodies.  Hardly  any  rich 
gold  deposit  is  left  in  the  long  inhabited  countries,  but  history 
and  myth  show  they  were  once  as  rich  in  gold,  as  California 
and  Australia  in  the  middle  of  this  century.  Gold  has  the 
brilliant  luster  (metallic)  in  a high  degree;  its  color  is  yellow- 
.ish;  its  density  almost  twenty  times  that  of  water;  when 
struck  a blow,  it  yields  (is  malleable).  Fire  does  not  change 
it;  it  is  rare,  it  cannot  be  overlooked  or  mistaken.  It  is  gold. 

3.  Primitive  man  also  found  another  metal  (luster,  mal- 
leable, heavy),  in  large  lumps,  grey  in  color.  We  have  record 
of  early  falls  from  heaven  of  such  masses  of  malleable  IRON 


9G 


LECTURE  6. 


at  Aegos  Potamos  on  the  Bosphorus.  Such  METEORITES  are 
represented  on  ancient  medals  and  coins.  In  the  time  of 
Homer  iron  was  prized  with  gold.  Many  large  meteoric  iron 
masses  have  been  found  in  Mexico,  near  the  Texas  border; 
also  in  Southeast  Africa,  where  the  natives  worked  them  into 
tools.  (J.  Herschel).  Atlas,  pp.  44,  45. 

4.  To-day,  THE  WORLD  produces  175  tons'  of  GOLD  a 
year  (49  in  U.  S.,  46  Australia,  15  Transvaal,  40  Russia  in 
1890;  now  Transvaal  much  more).  In  the  same  year  (1890) 
the  total  production  of  IRON  was  27  million  tons,  (U.  S.  10, 
England  8,  Germany  5,  France  2).  This  enormous  increase 
in  the  production  of  iron  is  directly  due  to  chemical  progress. 
The  price  in  Germany  was  (1890)  down  to  12  dollars  a ton. 

5.  THE  UNITED  STATES  produced,  in  1895,  71  tons  of 
GOLD  worth  47  million  dollars,  and  9.5  million  tons  of  IRON 
worth  105  million  dollars.  Accordingly,  the  ratio  of  the 
weights  of  iron  and  gold  possessing  equal  value  is  60,000  to  1. 
With  the  progress  of  smelting  this  ratio  has  been  rapidly  in- 
creasing during  the  ages,  and  is  bound  to  increase  still  more. 

6.  In  addition  to  these  two  METALS,  the  ancients  knew 
only  five  other  bodies  possessing  metallic  luster  and  mallea- 
bility; namely  silver,  copper,  tin,  lead  and  mercury.  For 
almost  two  thousand  years  these  SEVEN  METALS  were  com- 
pared to  the  seven  planets  and  designated  by  the  planetary 
signs:  Gold,  Sun;  silver.  Moon;  quicksilver.  Mercury;  cop- 
per, Venus;  iron.  Mars;  tin,  Jupiter;  lead,  Saturn.  Terms  in 
common  use  still  remind  us  of  this  comparison.  Atlas,  p.  43. 

7.  Chemists  now  designate  the  metals  by  the  CHEMICAL 
SYMBOLS  introduced  by  BERZELIUS  and  consisting  of  the 
first  and  the  characteristic  letters  of  their  latin  (or  latinized) 
name.  Thus  gold  (aurum).  An;  silver  (argentum),  Ag; 
quicksilver  (hydrargyrum),  Hg;  copper  (cuprum),  Cu;  iron 
(ferrum),  Fe;  tin  (stannum),  Sn;  lead  (plumbum),  Pb.  In 
a like  manner,  sulphur  is  represented  by  S,  Carbon  by  C,  and 
Iodine  by  lo.  Atlas,  p.  22. 


METALS,  OLD  AND  NEW. 


97  • 


8.  The  seven  old  metals  remain  even  to-day  THE  GREAT 
METALS  in  the  economic  life  of  nations.  Thus  the  United 
States  produced  in  1895  in  all  270.5  million  dollars  in  metals, 
of  which  iron  105.2;  silver  60.8;  gold  47.0;  copper  38.7;  lead 
10.7;  zinc  6.3;  mercury  1.3  million  dollars.  Here  we  have 
the  big  seven  of  old,  with  the  exception  of  tin,  replaced  by  the 
modern  zinc. 

9.  These  seven  old  metals  are  easily  DISTINGUISHED. 
Mercury  is  a heavy  liquid,  silvery  white.  Tin  and  lead  are 
readily  fusible;  color  and  gravity  distinguish  them:  Sn, 
white,  7.2;  lead,  bluish-gray,  11.4.  The  three  most  lustrous 
and  malleable  metals  melt  in  the  blowpipe  flame,  and  are  dis- 
tinguished by  color  and  gravity:  Cu,  red,  8.8;  Ag,  white, 
10.5;  Au,  yellow,  19.4.  Iron  is  infusible  in  the  blowpipe 
flame,  grayish- white,  and  has  G 7.8;  it  is  also  magnetic. 

10.  Zinc  (Zn)  was  known  to  ALCHEMISTS  in  the  15th  cen- 
tury; it  is  a metal,  but  malleable  only  at  a moderate  range 
of  temperature  (100  to  130  degrees);  melts  at  415,  G 6.9; 
boils  940.  The  readily  fusible  and  quite  volatile  metals  Ar- 
senic (As),  Antimony,  (Stibium,  Sb)  and  Bismuth  (Bi)  are 
so  brittle  that  they  can  be  pulverized;  color  and  gravity  will 
distinguish  them : As,  corroding  black,  5.7 ; Sb,  is  white,  6.7 ; 
Bi,  reddish-white,  9.8.  Probably  at  some  temperature  these 
will  show  malleability. 

11.  DURING  LAST  CENTURY  the  very  heavy  (21.5)  white 
metal  Platinum  (Pt),  infusible  in  the  blowpipe  flame,  was 
found  in  Brazil.  The  lighter  (11.4)  companion  Palladium 
(Pd)  was  distinguished  by  Wollaston,  1803.  Nickel  (Ni)  and 
Cobalt  (Co)  are  rare  companions  of  iron,  equally  infusible  in 
the  blowpipe  flame,  almost  equally  magnetic,  but  heavier 
(8.8)  and  whiter;  Ni  corrodes  green,  Co  pinkish-red.  Manga- 
nese (Mn)  and  chromium  (Cr)  also  resemble  iron,  but  are  not 
yet  used  as  metals. 

12.  Near  the  beginning  of  the  present  century  a number  of 
LIGHT  METALS  (G  less  than  5)  were  discovered;  the  follow- 


98 


LECTURE  6. 


ing  have  lately  come  into  use.  Aluminium  (Al)  quite  white, 
like  silver,  has  F 625,  G 2.56,  and  does  not  corrode  in  dry 
air.  Magnesium  (Mg),  grayish -white,  F 420,  G 1.75;  burns 
most  brilliantly  to  a white  ash  when  lit  by  a match.  Finally 
the  silver  white  metals  sodium  (Natrium,  Na)  and  potassium 
(Kalium,  Ka)  cannot  be  kept  in  air,  are  lighter  than  water,  in 
contact  with  which  they  burn. 


Notes  3. — The  great  Iowa  Meteor  (10:20  P.  M.,  February  12,  1875) 
was  seen  throughout  the  territory  extending  from  St.  Louis  to  St.  Paul 
and  from  Chicago  to  Omaha.  Its  explosion  was  heard  over  the  ten 
thousand  square  miles  of  Iowa  shaded  on  the  map,  p.  44. 

The  meteorites  fell  in  Iowa  County,  Iowa,  scattered  over  an  elliptic 
area  extending  nearly  ten  miles  from  southeast  to  northwest,  and  almost 
three  miles  across  at  the  widest.  The  greatest  stones  (all  containing 
over  ten  per  cent  of  native  nickelliferous  iron  in  granular  form)  fell 
between  the  seven  towns  of  the  Amana  Colony;  hence  the  name  Amana 
Meteorites.  I made  seven  collections,  aggregating  over  five  hundred 
pounds;  four  of  these  groups  are  well  shown  on  page  45  of  the  Atlas. 
The  two  largest  (Nos.  22  and  33)  were  not  my  own  property,  but  en- 
trusted to  me  for  study  and  protection.  The  largest  stone  weighs  seven- 
ty five  lbs.  (No.  33)  ; the  smallest  two  oz.  (No.  32). 

The  following  specimens,  arranged  in  decreasing  order  of  weight, 
were  presented  by  the  author  to  the  principal  mineralogical  museums  of 
Europe:  No.  i,  Paris  (5  kilos,  nearly);  2,  London;  ii,  St.  Petersburg; 
4,  Vienna;  13,  Brussels;  5,  Copenhagen;  14,  Harlem;  6,  Berlin;  15, 
Paris  (second  specimen,  over  2 kilos)  ; 7,  Christiania;  8,  Stockholm  ; 16, 
Munich;  and  No.  9,  Lausanne  (i  kilo). 

The  specific  gravity  ranged  from  3.45  to  3.50. 

Meteorites,  entering  our  atmosphere  from  space  beyond,  are  the 
only  cosmical  substances  accessible  to  the  chemist;  hence  their  extra- 
ordinary importance.  They  range  from  pure  nickelliferous  irons  to 
STONES  almost  destitute  of  metallic  iron. 

The  oldest  collection  of  meteorites  is  at  Vienna.  It  was  mainly  de- 
veloped by  Haidinger  (p.  28),  and  is  now  again  rapidly  growing  under 
Br^zina.  It  contains  500  distinct  localities,  of  which  320  are  stones;  the 
total  weight  is  three  tons  and  a half.  The  collection  of  meteorites  at  the 
Museum  of  the  Jardin  des  Plantes  at  Paris  was  greatly  developed  under 
the  care  of  the  eminent  Daubree,  and  is  now  in  charge  of  Meunier.  The 
grand  collection  of  the  British  Museum  at  London  is  in  charge  of 
Fletcher.  The  London  collection  is  the  richest,  because  of  the  vast  ex- 


METALS,  OLD  AND  NEW. 


1)9 


tent  of  the  empire  in  which  the  sun  never  sets,  and  because  English 
intelligence  is  ever  ready  to  part  with  British  gold  to  secure  prime  ma- 
terials for  science.  Thus  they  possess  the  largest  meteoric  iron  from 
Cranbourne,  Australia,  weighing  ten  tons;  and  their  gold  secured  the 
most  remarkable  Estherville  meteorite  (May  lo,  1879)  from  this  land  of 
millionaires.  However,  this  meteorite  was  drawn  up  from  its  wet  hiding 
place  for  my  study,  before  it  left  this  country. 


7.  CALCINATION  AND  REDUCTION. 

1.  GOLD  heated  on  charcoal,  in  the  fusing  point  of  the 
blowpipe  flame,  will  promptly  melt  to  a metallic  globule,  but 
suffer  no  other  change.  When  cold,  it  retains  the  globular 
form,  has  all  its  original  properties,  and  lost  nothing  in  weight. 
It  has  been  TRIED  BY  FIRE.  (1  Pet.  1.7;  Rev.  3,  18).  It 
remains  the  king  of  metals;  a metallic  globule  obtained  by  the 
blowpipe  is  still  called  a regulus,  and  pure  metals  are  called 
reguline,  as  of  old. 

2.  Silver  melts  like  gold,  but  loses  slightly  in  weight;  a 
small  amount  of  a metallic  calx  is  deposited  as  a reddish  IN- 
CRUSTATION on  the  charcoal.  Heat  this  incrustation  for  an 
instant  with  a good,  steady,  inner  flame,  and  minute,  brilliant 
white  silver  globules  will  appear.  The  calx  has  been  reduced 
again  to  reguline  silver.  Mercury  completely  volatilizes  in 
the  blowpipe  flame. 

3.  Copper  melts  like  gold  and  silver.  The  globule  re- 
mains red  in  the  inner  flame,  tinging  that  flame  green,  while 
in  the  outer  flame  the  globule  turns  black  on  the  surface. 
This  copper  ash,  scraped  off,  gives  reguline  copper  in  the 
inner  flame. 

Most  other  metals  are  much  more  readily  CALCINED,  and 
correspondingly  more  difficultly  REDUCED. 

4.  Exposing  a fragment  of  LEAD  on  charcoal  to  the  blow- 
pipe flame,  it  melts  almost  instantly,  boils,  and  burns  with  a 
bluish  flame  to  a calx  or  ash  (Litharge)  which  forms  quite  a 


100 


LECTURE  7. 


large  yellowish,  incrustation  on  the  charcoal.  If  the  outer 
flame  is  used  for  some  time,  the  incrustation  will  be  reddish 
(red  lead),  and  all  metallic  lead  will  be  calcined. 

5.  This  lead  incrustation,  heated  in  the  inner  flame,  almost 
instantly  yields  a multitude  of  minute  globules  of  metallic  lead 
(reguli),  readily  recognized  as  such  by  color,  softness  and 
malleability. 

Thus  lead  is  readily  calcined  in  the  outer,  and  reduced  in  the 
inner  flame.  This  change  from  metal  to  calx,  and  reduction 
from  calx  to  regulus,  may  be  repeated  any  number  of  times. 

6.  Lead  containing  some  silver  will  leave  that  silver  as  a 
pure  regulus,  while  the  lead  is  calcinated  in  the  outer  blowpipe 
flame.  In  this  manner  much  of  the  silver  has  been  extracted 
from  argentiferous  lead  from  time  immemorial ; the  process  is 
called  CUPELLATION.  The  name  litharge  (lith-argyros, 
silver  stone)  still  in  use  points  to  the  antiquity  of  this  process. 
On  a porous  support  (bone  ash  cupel)  it  works  better  than  on 
charcoal,  the  melted  calx  soaking  into  the  cupel. 

7.  TIN  heated  on  charcoal  in  the  outer  flame  melts  and 
forms  a white  incrustation  due  to  its  calcination.  This  in- 
crustation can  be  reduced  to  a regulus,  especially  after  mixing 
the  calx  with  a little  soda  and  borax.  Aiding  reduction  to  the 
metallic  state,  soda  alone  or  with  borax,  is  spoken  of  as  a 
REDUCING  FLUX. 

8.  A fragment  of  ZINC  is  so  promptly  calcinated  in  the 
outer  flame  that  its  fusion  is  usually  not  noticed.  It  burns 
with  a brilliant  green  flame  and  deposits  a large  incrustation 
which  (as  well  as  the  RESIDUE  of  calx  left  where  the  metal 
was)  is  infusible,  yellow  while  hot,  and  turns  white  on 
cooling.  This  change  in  color  can  be  indefinitely  renewed  by 
repeated  heating. 

9.  MAGNESIUM  burns  with  extreme  brilliancy,  leaving  a 
pure  white,  infusible  residue  of  calx.  ALUMINIUM  burns  also, 
but  much  less  readily;  its  calx  is  also  white  and  infusible. 


CALCINATION  AND  REDUCTION. 


101 


These  white  infusible  masses  cannot  be  reduced  by  the 
blowpipe,  but  are  readily  distinguished  by  igniting  them  after 
the  addition  of  a drop  of  COBALT  SOLUTION.  The  calx  from 
aluminium  will  become  deep  blue,  that  from  magnesium  pale 
rose,  while  zinc  calx  treated  in  this  way  becomes  green. 

10.  The  metals  As,  Sb,  Bi  burn  readily  and  leave  an  ash. 
The  most  volatile  ARSENIC,  emitting  the  odor  of  garlic,  dis- 
appears, leaving  but  a slight  white  incrustation  far  away  from 
the  sample.  ANTIMONY  melts  to  a globule  and  burns  with 
a white  smoke,  rising  straight  up  from  the  sample  when  the 
flame  is  withdrawn ; when  the  burning  globule  is  dropped  on 
the  table,  it  breaks  into  many  small  globules,  each  leaving  a 
white  trail  of  the  calx.  BISMUTH  gives  a yellow  incrustation. 
When  reduced,  both  antimony  and  bismuth  are  brittle,  dis- 
tinguishing them  from  tin  and  lead. 

11.  IRON  heated  in  the  outer  flame  gives  a black  residue, 
no  incrustation;  when  again  exposed  to  the  inner  flame  (best 
with  soda)  only  gray,  MAGNETIC  grains  or  spangles  are  ob- 
tained. COBALT  and  NICKEL  act  in  a like  manner. 

They  are  however  readily  distinguished  by  fusing  a little 
of  the  calx  into  a borax  bead.  Iron  will  make  the  bead 
yellowish  in  the  outer,  colorless  in  the  inner  flame;  nickel 
gives  a brownish  bead,  and  with  cobalt  the  bead  shows  a 
splendid  deep  blue  color.  The  chromium  beads  are  green, 
those  containing  manganese  are  amethyst  in  the  outer,  colorless 
in  the  inner  flame. 

12.  The  light  metals  SODIUM  and  POTASSIUM  should  not 
be  burnt  in  the  blowpipe  flame;  it  would  be  very  dangerous. 
They  leave  white,  fusible  residues,  coloring  the  flame  yellow 
(Na)  or  purple  (Ka). 

Thus  all  metals  may  be  readily  distinguished  in  a few  in- 
stants by  the  blowpipe,  even  if  they  are  calcinated  or  otherwise 
combined.  These  fire-tests  or  PYROGNOSTIC  CHARACTERS 
of  the  metals,  should  be  familiar  to  all  who  wish  to  study 
chemistry.  They  are  the  most  ready  and  distinct  means  for 
the  recognition  of  the  metals  under  all  conditions. 


8.  ALLOYS  AND  AMALGAMS. 


1.  The  different  metals  can  be  melted  together  in  various 
proportions  forming  ALLOYS,  several  of  which  have  been  in 
common  use  from  time  immemorial,  such  as  bronze  and  brass. 
If  one  of  the  metals  is  mercury,  the  alloy  is  called  an  AMALGAM. 

2.  The  readily  fusible  white  metals  are  very  soluble  in 
mercury.  Lead,  antimony,  bismuth  and  even  silver,  dissolve 
so  readily  and  abundantly  in  mercury  as  to  cool  the  mass,  over 
20  degrees  (down  to  16  below  zero) . The  tin  amalgam  is  used 
as  a coating  on  glass  for  mirrors. 

Iron  is  insoluble  in  mercury;  so  are  the  other  metals 
infusible  before  the  blowpipe,  like  platinum.  Accordingly, 
mercury  is  shipped  in  iron  flasks,  each  holding  35  kilos. 

3.  Gold  is  about  as  soluble  in  mercury  as  silver.  The 
GOLD  AMALGAM  is  solid  at  common  temperatures,  and  can  be 
separated  by  wringing  out  the  chamois  into  which  the  mercury 
and  amalgam  has  been  poured;  the  mercury  will  run  through, 
the  solid  amalgam  remaining.  The  amalgam  loses  about  one 
third  of  its  weight  on  heating,  or  contains  two  parts  of  gold  to 
one  of  mercury. 

4.  The  bulk  of  all  the  mercury  produced  (about  4000  tons 
a year)  is  used  for  the  EXTRACTION  of  GOLD  and  SILVER. 
Gold  sand  is  concentrated  by  washing,  the  lighter  materials 
being  removed  farthest.  When  sufficiently  concentrated,  the 
remaining  heavy  material  is  treated  with  mercury,  which  dis- 
solves the  gold.  The  excess  of  mercury  is  separated  as  above 
from  the  gold  alloy,  which  then  by  heat  is  freed  from  the 
mercury. 

5.  SOLDER,  for  tin  ware,  is  an  alloy  of  equal  parts  of  tin 
and  lead,  melted  together  in  an  iron  ladle.  It  melts  at  about 
190  degrees,  which  is  40  degrees  below  the  fusing  point  of  tin, 
the  most  fusible  of  the  two  ingredients.  In  general,  the  alloys 
are  more  fusible  than  their  constituents. 


ALLOYS  AND  AMALGAMS. 


103 


6.  The  most  important  of  all  alloys  in  the  history  of  man- 
kind is  BRONZE,  containing  about  one  part  of  tin  to  nine  of 
copper.  In  ancient  days  it  was  smelted  direct  from  a mixture 
of  copper  and  tin  ores,  or  by  adding  tin  ore  to  melted  copper. 
By  slow  cooling  it  hardens,  by  sudden  cooling  it  becomes  mal- 
leable (contrast  with  steel). 

7.  The  ancients,  from  the  Egyptians  to  the  Romans,  made 
WEAPONS,  TOOLS  and  ORNAMENTS  of  bronze.  Until 
recently,  canons  were  made  of  bronze ; now  it  is  used  for 
statuary,  bells,  medals  and  ornamental  work.  The  copper  is 
first  melted,  then  the  tin  added  in  reasonable  excess,  to  allow 
for  loss  by  combustion. 

8.  BRASS  (yellow)  is  an  alloy  of  two  parts  of  copper  with 
one  of  zinc.  It  can  be  cast,  hammered,  rolled  and  drawn  and 
thus  is  most  readily  shaped  into  any  form.  It  was  used  before 
zinc  was  known,  by  adding  the  mineral  cadmia  (a  zinc  ore)  to 
molten  copper.  By  adding  an  amount  of  nickel  equal  to  that 
of  zinc  to  the  brass,  German  silver  results. 

9.  TYPE  METAL  consists  of  lead  about  4 and  antimony 
1 part,  with  some  tin.  It  is  very  readily  fusible,  and  expands 
upon  solidification  (as  does  water  on  freezing),  thus  filling  the 
form  exactly  to  the  minutest  detail. 

Very  fusible  alloys  contain  bismuth.  Thus  Darcet’s  Metal, 
melting  in  the  steam  over  boiling  water,  consists  of  bismuth  8, 
lead  5,  tin  3 parts;  it  melts  at  94  degrees. 

10.  The  most  characteristic  modern  alloy  is  ALUMINIUM 
BRONZE  (copper  9,  aluminium  1 part),  which  is  very  light 
and  resembles  gold  in  appearance.  Ferroaluminium  contains 
9 iron  to  1 aluminium;  it  is  much  stronger  than  the  above. 

11.  Native  gold  generally  contains  some  silver.  Australian 
gold  averages  7 per  cent.,  Californian  gold  averages  12  per  cent, 
of  silver,  and  is  light  yellow.  VVith  about  20  per  cent,  it  is 
called  Electron,  the  ASEM  of  the  ancient  Egyptians.  From 
this,  pure  gold  or  pure  silver  was  obtained  at  will.  The 


104 


LECTURE  9. 


alloys  seemed  to  show  that  metals  were  variable  and  thus 
gave  some  encouragement  to  the  alchemists. 

12.  When  the  Egyptians  had  learned  to  separate  silver 
from  gold,  they  dropped  Asem  from  their  list  of  metals.  Their 
method  of  separation,  described  in  the  Leyden  papyri,  is 
essentially  the  same  dry  way  process  used  till  the  present. 
The  active  agents  were  calcined  green  vitriol  and  salt,  as  in 
the  ROYAL  CEMENT  of  the  alchemists. 


9.  ORES  AND  CLEAVAGE. 

1.  ORES  ARE  MINERALS  FROM  WHICH  METALS  CAN  BE 
PROFITABLY  OBTAINED.  Every  student  in  chemistry  should 
know  at  least  the  principal  ores  from  which  already  the 
ancients  and  the  alchemists  extracted  the  metals;  he  should 
be  able  to  recognize  them  at  sight  and  by  handling  them.  To 

.help  him  do  so  is  the  object  of  this  lesson. 

2.  Ores  are  generally  distinguished  from  other  minerals  by 
a HIGH  GRAVITY  (4  and  over)  associated  with  LOW  HARD- 
NESS. Very  few  have  a 
hardness  equal  to  glass  (de- 
gree 5) , that  is,  able  to  scratch 
glass  and  be  equally  scratched 
by  it.  Many  have  the  hard- 
ness of  copper  (3)  only. 
METALLIC  LUSTER  is  fre- 
quent; in  that  case,  the  color 
is  constant  and  therefore 
specific.  If  the  luster  is  not 
metallic,  the  color  is  gen- 
erally variable. 

3.  THE  BLOWPIPE  will  promptly  reveal  the  presence  and 
nature  of  the  metal  in  the  ore.  It  will  also  show  whether  the 
ore  is  a sulphide  or  not;  the  former  emit  the  odor  of  burning 


AGRICOLA. 


ORES  AND  CLEAVAGE. 


105 


sulphur  while  heated.  This  test  may  be  made  by  simply 
heating  the  mineral  in  an  open  glass  tube,  held  slanting  in 
the  Bunsen  flame.  Some  sulphides  also  yield  a sublimate  of 
white  arsenic  and  give  the  odor  of  garlic. 

4.  Accordingly,  the  ORES  are  readily  DISTINGUISHED  as 
sulphides  and  free  from  sulphur.  The  last  are  either  native 
metals  or  calxes.  The  first  are  either  simple  sulphides  or  con- 
tain arsenic  also.  We  will  give  the  principal  distinctive  prop- 
erties for  each  of  the  common  ores. 

5.  NATIVE  METALS  are  distinguished  by  their  luster  and 
malleability  (flattening  under  the  blow  of  a hammer) . They 
give  no  odor  of  either  sulphur  or  arsenic  before  the  blowpipe. 
Gravity  and  color  distinguish  them  one  from  the  other.  G 17 
to  19:  Au,  yellow;  Pt,  white;  11,  Pd,  white;  10,  Ag, 
white;  Bi,  reddish  gray  and  rather  brittle;  8.5,  Cu,  red;  8, 
Fe,  white,  only  in  meteorites. 

6.  The  CALXES  are  without  metallic  luster,  either  dull  or 
sub-metallic.  HARD  enough  to  scratch  glass  (over  5)  readily, 
are:  G 6,  CASSITERITE,  brown,  and  brownish  streak  (streak 
is  the  color  of  the  powder,  or  trace  on  rough  porcelain),  con- 
tains Sn;  G 5,  contain  Fe;  streak:  Black,  MAGNETITE;  red, 
HEMATITE. 

7.  Calxes  not  hard  enough  to  scratch  glass,  but 
scratching  copper  readily,  are  quite  numerous,  and  have  all  a 
specific  gravity  of  about  4.  Hence  they  are  to  be  distinguished 
by  color  (first  named)  and  streak  (second) : red,  orange, 
LlMONlTE  (Fe)  ; red,  brownish-red,  CUPRITE  (Cu)  ; reddish, 
orange,  ZINCITE  (Zn)  ; grayish,  white,  SMITHSONITE  (Zn)  ; 
brownish,  gray,  SlDERlTE  (Fe);  green,  green,  MALACHITE 
(Cu).  GARNIERITE,  the  modern  nickel  ore,  is  green  and 
harder  than  Malachite;  blackish-gray,  black,  PYROLUSITE 
(Mn). 

8.  SULPHIDES  HARD  enough  to  scratch  glass  readily,  but 
resisting  the  knife,  have  all  marked  metallic  luster  and  there- 
fore are  easily  distinguished  by  their  color.  Yellow,  PYRITE 


106 


LECTURE  9. 


(Fe,  no  As).  The  following  contain  arsenic  and  are  distin- 
guished by  their  color  and  gravity:  Gray,  (6)  ARSENO- 
PYRITE;  white  (8),  LEUCOPYRITE,  and  red  (7.5)  NlCCO- 
LITE  (copper  nickel,  the  old  nickel  ore). 

9.  SULPHIDES,  NOT  HARD  enough  to  scratch  glass,  readily 

yielding  to  the  knife  edge,  have  either  brilliant  metallic  luster 
or  not.  By  their  gravity  and  color  they  are  readily  distin- 
guished as  follows;  the  metal  they  yield  before  the  blowpipe 
being  added.  Brilliant  metallic  luster;  gravity : 7.5,  GALE- 

NITE,  gray,  Pb;  5,  TETRAHEDRITE,  gray,  much  As,  some 
Ag;  4.5  STIBNITE,  blackish -gray,  Sb;  4,  CHALCOPYRITE 
(copper  pyrite),  brass-yellow,  Cu.  Without  metallic  luster; 
gravity:  9,  CINNABAR,  red,  Hg;  4,  SPHALERITE,  blackish 
to  yellow,  Zn;  3.5  ORPIMENT,  yellow.  As;  3,  REALGAR, 
red.  As.  GRAPHITE  (C)  and  SULPHUR  (S)  are  readily  dis- 
tinguished from  sulphides. 

10.  Almost  every  specimen  of  galenite  shows  many  plane, 
brilliantly  reflecting  surfaces.  If  struck  by  a hammer,  it  will 
break  according  to  such  plane  surfaces  only,  with  extreme 
readiness;  we  say  it  has  perfect  CLEAVAGE.  There  will  be 
seen  three  such  cleavage  planes,  mutually  under  a right  angle. 
This  is  most  characteristic  of  gale’nite.  Magnetite  shows  four 
cleavage  planes;  fine  specimens  of  Sphalerite  even  six.  Orpi- 
ment  has  one  cleavage  only,  according  to  which  it  will  split 
into  thin  foli«.  Pyrite  is  entirely  destitute  of  cleavage. 

11.  Choice  specimens,  taken  from  the  walls  of  some  cavity, 
where  the  substances  were  free  to  grow,  show  beautiful 
geometrical  forms,  all  bounded  by  plane  surfaces  only.  Such 
specimens  are  CRYSTALS.  Galenite,  corresponding  to  its 
cleavages,  shows  cubes,  often  with  the  corners  equally  cut  off 
(truncated) ; p.  66,  fig.  2.  Magnetite  and  Cuprite  show 
octahedrae;  p.  58,  59.  Tetrahedrite  shows  modifications  of 
half-octahedrae,  or  tetrahedrse ; p.  66,  figs.  16,  9.  ITematite, 
especially  from  Elba,  shows  splendid  six  and  twelve  sided 
forms  (Elba  Roses),  p.  57. 


ORES  AND  CLEAVAGE. 


107 


12.  Pyrite  quite  frequently  is  crystallized.  Its  simplest 
and  most  common  form  is  the  cube,  bounded  by  six  equal 
squares  (p.  66,  fig.  1).  Upon  inspection  these  squares  are 
usually  found  to  be  striated  parallel  to  one  side.  Examining 
the  three  squares  meeting  at  one  corner,  these  striations  will 
be  found  parallel  to  the  three  edges  meeting  at  that  corner, 
(p.  54,  figs.  17  to  19).  In  many  cases  the  edges  are  beveled, 
and  finally  show  the  so-called  Pyritohedron  (p.  66,  fig.  21) 
bounded  by  twelve  five  sided  faces. 


Note.  The  portrait  of  Georg  Agricola  has  been  inserted  in  the 
text  of  this  lecture.  Agricola  was  called  the  father  of  mineralogy  by 
Werner,  a century  ago.  He  was  born  March  24,  1494  at  Glauchau, 
Saxony,  and  died  in  November,  1555,  at  Chemnitz,  Saxony.  He  settled 
in  the  new  mining  town  Joachimsthal,  Bohemia,  and  studied  everything 
pertaining  to  the  rich  silver  veins  which  made  that  town  and  region 
flourish.  His  works  on  metals  and  mining  are  the  first  which  have 
appeared  during  modern  times;  they  are  noted  for  thoroughness  and 
accuracy.  The  portrait  is  a copy  of  Schrauf’s,  (Vienna  1894)  which  is  a 
reduction  from  Sambucus,  Antwerp,  1574,  plate  38. 


10.  CRYSTAL  GEMS. 

1.  The  old  egyptian  list  of  metals  contains  blue  (chesteb) 
and  green  (mafek)  gems  immediately  after  Gold  (nub),  Asem 
and  Silver  (hat),  and  followed  by  bronze  (chomt),  iron  (men) 
and  lead  (taht).  The  Egyptians  were  familiar  with  the  fact 
that  copper  tints  fluxes  blue  and  green;  but  they  distin- 
guished the  genuine  gems  easily  from  the  artificial  by  their 
hardness.  Moses  also  was  familiar  with  true  gems.  (Exod. 
28). — Gems  are  sold  by  the  CARAT  which  is  one-fifth  of  a 
gramme. 

2.  THE  TRUE  GEMS  (p.  46)  are  crystals. of  exceeding 
hardness.  To  be  prized  as  jewels  they  must  also  be  trans- 
parent and  either  absolutely  colorless  or  finely  colored. 
Hence,  good  instructive  specimens  are  obtainable  for  study 


108 


LECTURE  10. 


at  reasonable  rates,  while  the  price  of  the  same  materials 
fit  for  the  lapidary  may  be  beyond  reach.  Gems  do  not  differ 
much  in  specific  gravity;  accordingly,  this  property  is  of  little 
value  in  distinguishing  them. 

3.  The  gem  crystals  are  generally  well  formed,  and  their 
DEGREE  of  SYMMETRY  may  be  recognized  without  much  dif- 
ficulty. If  the  same  face,  as  to  inclination  and  position 
towards  the  direction  of  a more  or  less  marked  corner  or  prism, 
occurs  twice  only,  the  crystal  is  called  rhombic,  (pp.  61,  62) ; 
if  thrice,  rhombohedral,  p.  57;  if  four  times,  quadratic,  (p.  60), 
and  if  six  times,  hexagonal,  (Beryl,  p.  56).  If  the  same 
crystal,  held  in  two  different  positions,  shows  both  rhombohe- 
dral and  quadratic  symmetry,  it  is  called  tesseral  (pp.  58,  59). 
(For  mono-and  tri-clinic,  see  note). 

4.  The  degree  of  HARDNESS  of  quartz  is  called  7 ; that  of 
topaz  8,  of  corundum  9 and  of  the  diamond  10.  The  most 
precious  gems  possess  the  hardness  8 and  over;  namely  topaz 
8,  spinel  8,  chrysoberyl  8i,  ruby  and  sapphire  9,  diamond  10. 
Below  these  we  have  the  emerald  7f,  zircon  7j,  turmaline  7i 
and  the  “poor  man’s  gems”  garnet  and  quartz  7. 

5.  These  gems  are  also  CHEMICALLY  divisible  into  the 
same  two  groups.  All  of  lower  hardness,  including  topaz,  fail 
to  dissolve  in  a bead  of  microcosmic  salt  in  the  blowpipe  flame, 
precisely  as  do  glass  and  other  silicates ; to  that  extent  they 
are  natural  glasses,  crystalized.  But  the  harder  gems,  spinel, 
chrysoberyl  and  corundum  (sapphire  and  ruby)  do  dissolve, 
and  are  not  glass-like  (silicates). 

The  diamond  stands,  entirely  by  itself;  it  is  combustible 
under  special  conditions. 

6.  Quartz  crystals  (p.  65)  are  quite  abundant,  and  very 
often  perfectly  transparent  (rock  crystal)  ; if  purple,  amethyst, 
if  dark  wine  yellow,  smoky  quartz.  Its  hardness  is  taken  as 
the  standard  7.  Gravity  2.7 ; no  cleavage.  Symmetry 
rhombohedral;  commonly  a regular  six-sided  prism,  r,  striated 
crosswise  (Figs.  6,  7)  dominates,  terminated  by  the  three 


CRYSTAL  GEMS. 


lOJ) 


rhombohedral  faces,  P,  usually  alternating  with  a second 
smaller  set  of  rhombohedral  faces,  Z.  A little  experience  will 
enable  any  one  to  recognize  the  constancy  of  crystal  form  in 
the  apparently  infinite  variety  of  appearances  and  linear 
dimensions. 

7.  The  GARNET  (p.  59)  is  recognized  by  its  form,  being 
generally  a dodecahedron  (bounded  by  twelve  equal  rhombs, 
d),  inclined  under  a right  angle  over  the  long  diagonal,  and 
forming  a rhombohedron  of  120  degrees  at  the  three  sided 
corners.  Garnets  show  many  colors;  the  pyrope,  used  in 
jewelry,  is  deep  red. 

TURMALINE  crystals  have  a dominant  prism,  striated 
lengthwise,  surmounted  by  rhombohedral  faces;  usually  only 
one  termination  shows,  the  crystals  breaking  readily  cross- 
wise. Colors  varied,  often  in  belts  or  zones. 

8.  The  Zircon  (p.  60)  is  noted  for  quadratic  symmetry 
only;  fine  transparent  brownish  and  orange  crystals  are  used 
under  the  name  of  hyacinth. 

BERYLS  (p.  56)  are  quite  common  and  very  large,  forming 
regular  six-sided  prisms,  terminating  in  a base  at  right  angles 
thereto,  and  show  cleavage  after  this  plane.  Fine  beryls  are 
always  small  and  prized  as  AQUAMARINES  when  blueish ; 
when  bright  green,  they  are  the  most  valuable  EMERALD. 

9.  The  TOPAZ  (pp.  61,  62;  also  p.  67,  Fig.  43)  forms  a 
rhombic  prism  (M,  1),  striated  lengthwise,  and  possessing 
perfect  cleavage  crosswise  (i.  e.  basal,  P)  ; the  crystals  show 
generally  only  one  termination,  the  basal  plane  with  the  domes 
f and  y and  the  pyramid  i.  Yellowish  colors  are  most  common. 
The  shade  of  color  and  especially  the  character  or  habitus  of 
the  crystals  are  peculiar  to  each  principal  locality,  so  that  the 
expert  can  tell  from  the  habitus  and  color  whether  the  topaz 
came  from  Brazil,  Saxony,  Siberia  or  Japan. 

10.  SPINEL  is  tesseral,  the  octahedron  (bounded  by  eight 
equal  equilateral  triangles,  p.  58,  fig.  1)  dominating.  CHRY- 
SOBERYL  (p.  62,  Alexandrite)  is  rhombic;  but  its  prism  (119.8 


110 


LECTURE  10. 


degs.)  is  so  nearly  hexagonal  (120  degs.)  that  it  gener- 
ally occurs  in  six-sided  stellar  combinations.  A Russian  vari- 
ety, known  as  ALEXANDRITE,  is  emerald  green  in  reflected, 
deep  red  in  transmitted  light,  thus  showing  the  Russian  colors. 
Transparent  specimens  thereof  form  very  valuable  gems. 
Atlas,  p.  53. 

11.  CORUNDUM  (p.  56)  is  exceeded  in  hardness  by  the 
diamond  only,  so  that  it  readily,  is  distinguished  from  all 
other  bodies.  It  crystallizes  in  rhombohedral  forms,  usually 
showing  a double  pyramid,  terminated  by  a base,  o.  It  shows 
perfect  cleavage  according  to  its  base  and  a rhombohedron,  R. 
Transparent  crystals  of  corundum  are  next  to  the  diamond  in 
value;  when  blue  they  are  called  SAPPHIRE,  when  red  RUBY. 
Good  rubies  have  been  made  by  Fremy.  Impure  corundum, 
containing  hematite,  is  called  emery,  and  used  for  grinding 
and  polishing  steel. 

12.  The  DIAMOND  is  the  hardest  of  all  bodies;  it  crystal- 
lizes in  octahedrae  (p.  66,  fig.  9)  variously  modified  (figs.  11, 
12),  and  has  four  cleavage  planes  parallel  to  the  faces  of  the 
octahedron.  Imperfect  diamonds,  unfit  for  jewelry,  are  called 
bort.  Black  pebbles  of  diamond  hardness  are  called  carbonado 
and  used  for  rock  drills.  The  price  of  good  diamonds  increases 
approximately  as  the  square  of  the  number  of  carats.  Dia- 
monds have  been  made  by  Moissan  (p.  36). 


Notes — 2.  The  cost  of  gems  varies  greatly  according  to  quality. 
The  following  extract  from  the  price  list  of  a New  York  dealer  is  for 
^^fair  to  good  gems,  neither  poor  nor  the  best.”  The  price  is  given  in 
dollars  per  carat;  the  order  is  that  of  our  description. 

Quartz:  rock  crystal  3-1;  amethyst  'ii,— i ; garnet  ^-2 ; turmaline 
2-12;  zircon  2-8;  beryl,  golden  and  aquamarines  1-8;  emerald  10-80; 
topaz  i-5 ; spinel  8-48;  chrysoberyl  3-16;  alexandrite  24-96.  Corundum  : 
sapphire  3-24 ; ruby  8-96.  Diamond  50-150. 

3.  The  important  subject  of  Crystal  Symmetry  can  only  be  ap- 
proached by  the  beginner  when  aided  by  a good  atlas  of  crystal  forms. 
For  that  reason  18  plates  of  the  admirable  atlas  of  Nikolai  von  Kokscha- 


CRYSTAL  GEMS. 


Ill 


row^  accompanying  his  great  work:  Materialien  zur  Mineralogie  Russ- 
lands,  have  been  added  in  good  photo  reductions.  In  most  cases  each 
form  is  represented  first  in  perspective  and'  right  helow  in  horizontal 
projection;  the  first  is  marked  bv  the  number,  the  second  by  the  same 
number  and  the  word  bis  ” (twice,  second).  This  second  figure  shows 
the  symmetry  undisturbed  by  perspective,  and  should  be  specially  studied. 
Each  face  is  generally  designated  by  a letter. 

In  addition  to  the  five  degrees  of  symmetry  specified,  two  lower  forms 
exist,  namely:  moxoclinic,  having  only  symmetry  right  and  left,  in 
pyroxene,  p.  63  and  orthoclase  p.  64;  and  finally  triclinic,  having  no 
symmetry  whatever,  or  being  asj'mmetric,  see  Lepolith  (really  anorthite) 
p.  64. 

9.  Good  specimens  of  topaz  for  the  study  of  rhombic  crystal  form  are 
comparitively  cheap;  the  basal  cleavage  avoids  the  possibility  of  mistakes. 

The  three  plates  copied  from  Kokscharow  show  some  of  the  finest 
topaz  crystals  in  their  true  form,  each  face  exactly  as  it  is  developed. 
The  scale  of  our  plates  is  almost  one-half  of  the  original;  exactly  0.44  or 
nine-twentieths.  See  pages  61,  62,  where  the  plates  are  designated  by 
the  letters  a,  d and  f at  the  right  hand  top. 

On  page  61  (a  and  d)  figures  58,  59  and  67  represent  (half  size) 
splendid  topaz  crystals  from  Nertschinsk,  Siberia  ("Vol.  Ill,  p.  207). 
They  are  transparent,  dark  wine  yellow.  The  crystal  fig.  59  weighs  1.6 
kilograms. 

On  page  62  (f)  is  given  (fig.  76)  the  horizontal  projection  (half  natural 
size)  of  the  finest  and  largest  topaz  crystal  yet  obtained.  It  is  28  cm 
high,  16  and  12  cm  across,  and  weighs  10.2  kilograms.  Von  Kokscharow 
(III  378)  says:  a topaz  crystal  of  so  extraordinary  size  and 

beauty  as  has  never  been  seen  before.  This  crystal  belongs  to  the  greatest 
rarities  of  the  mineral  kingdom,  on  account  of  its  extraordinary  magni- 
tude, perfection  of  crystallization,  fine  color  (dark  wine  yellow)  and 
transparency.”  It  was  found  in  the  Nertschinsk  region,  in  the  mountains 
near  the  Urulga  river,  Transbaikalia,  Siberia;  was  presented  to  Emperor 
Alexander  II  in  i860,  and  is  deposited  in  the  Mineralogical  Museum  of 
the  Mining  Institute  of  St.  Petersburg. 

10.  The  group  of  Alexandrite  crystals  represented  (p.  53)  is  one  of 
the  most  magnificent  specimens  of  native  crystals  (v.  Kokscharow,  Vol. 
IV,  p.  62).  The  group  contains  22  large  and  finely  formed  twin  crystals; 
the  group  is  25  cm  long,  14  cm  high  and  ii  cm  wide,  and  weighs  over  5 
kilograms. 

The  Gems.  Page  46,  shows  the  common  crystal  form  of  the  following: 

I,  diamond;  2,  sapphire;  3,  ruby;  4,  amethyst;  5,  emerald;  6,  garnet;  7, 
aquamarine;  8,  topaz;  9,  peridot  or  olivine,  chrysolite;  10,  rock  crystal; 

II,  turmaline.  This  plate  is  a half-tone  reduction  from  the  fine  colored 
plate  V of  Simonin,  Les  pierres,  Paris,  1869. 


11.  CRYSTAL  STONES. 


1.  THE  RECOGNITION  OF  ANY  MATERIAL  by  means  of 
its  physical  properties  is  a habit  that  must  be  cultivated  by 
every  one  who  would  study  chemistry  successfully.  Incident- 
ally the  student  becomes  practically  acquainted  with  a number 
of  those  minerals  on  which  the  chemist  depends  for  his  ma- 
terials— and  even  for  the  very  ideal  of  chemical  individuality. 

2.  The  following  dozen  STONES  should  be  so  familiar  to 
every  student  that  he  can  recognize  them  promptly  in  any  of 
their  varied  forms.  As  a group  they  are  not  as  hard  as  the 
gems,  nor  as  heavy  as  the  ores.  H 6 and  G 4,  are  the  limits. 
The  dozen  selected  are  the  most  important  practically,  and  the 
best  marked  physically  and  crystallographically.  Good  speci- 
mens can  be  had  at  comparatively  little  outlay;  many  can  be 
collected. 

3.  To  recognize  a substance,  its  properties  should  be 
observed  in  a DEFINITE  ORDER.  First  (by  sight)  luster,  then 
color  and  streak;  next  (by  handling),  hardness  and  by  mere 
lifting  an  estimate  of  the  specific  gravity  is  obtained.  Then 
the  specimen — if  not  a crystal — should  be  broken  by  a blow; 
that  will  reveal  fracture  or  cleavage;  in  the  latter  case,  the 
number,  relative  position  and  degree.  Finally,  if  crystal  faces 
visible,  they  should  be  examined  with  a view  to  determine 
the  symmetry  of  the  crystal.  In  that  case,  cleavage  planes 
are  often  revealed  by  existing  cracks. 

4.  The  last  five  of  the  minerals  selected  are  SILICATES, 
that  is,  they  leave  an  insoluble  silica  skeleton  in  the  micro- 
cosmic  bead  (10,  5);  they  are  among  the  most  common 
constituents  of  the  hard  rocks,  such  as  granites.  The  others 
are  not  silicates.  The  first  alone  is  soluble,  its  taste  reveals 
its  nature,  salt;  the  merest  trifle  of  it  tinges  the  blowpipe 
flame  persistantly  and  intensely  yellow  (Na).  The  next  five 
tinge  the  flame  orange,  appearing  siskin -green  through  a green 
glass;  they  contain  calcium  (Ca).  The  heaviest  tinges  the 
flame  yellowish  green;  it  contains  the  metal  barium  (Ba). 


CRYSTAL  STONES. 


113 


5.  TABULAR 

STONES— 

VIEW 

OF  THE  PROPERTIES 

OF  A DOZEN 

No. 

Name. 

n. 

G. 

Cleavage. 

Crystal  Synimetrj’. 

I. 

Halite, 

2 

2.2 

3 pfct.,  90  degs. 

Tesseral. 

2. 

Gypsum, 

2 

2-3 

I em.,.2  pfct.. 

Monoclinic. 

3* 

Calcite, 

3 

2.6 

3 perfect,  105  degs. 

Rhombohedral. 

4- 

Aragonite, 

3h 

2.9 

I imperfect. 

Rhombic. 

5* 

Fluorite, 

4 

3-1 

4 perfect,  octah. 

Tesseral. 

6. 

Apatite, 

5 

3-1 

I imperfect. 

Hexagonal. 

7' 

Barite, 

3 

4-5 

I pfct.,  2 less  so. 

Rhombic. 

S. 

Mica. 

2 

2.9 

I eminent. 

Six-sided. 

9* 

Amphibole, 

3-^ 

2 pfct.,  nearly  120  degs. 

Monoclinic. 

lO. 

Pyroxene, 

3-3 

2 pfct.,  nearly  90  degs. 

Monoclinic. 

II. 

Feldspar, 

6 

2-5 

2 pfct.,  nearly  90  degs. 

Mono  ortriclin. 

12. 

Quartz, 

7 

2.7 

no  cleavage. 

Rhombohedral. 

6.  All  of  these  stones  are  destitute  of  metallic  LUSTER, 
that  property  being  peculiar  to  metals  and  ores.  The  luster 
is  dull  or  vitreous  according  to  the  perfection  of  the  specimen. 
If  ONE  CLEAVAGE  eminent,  so  perfect  that  it  can  be  split 
into  thin  leaves  (Nos.  2,8)  the  luster  will  appear  pearly, 
which  is  noted  even  on  the  best  cleavage  of  feldspar  (No.  11.) 

7.  These  minerals  are  generally  colorless  or  white;  but  as 
they  have  no  metallic  luster,  their  COLOR  VARIES  according 
to  impurities  admixed,  whether  organic  or  inorganic.  Thus 
Halite  (Rock  Salt)  and  Fluorite  (Fluorspar)  show  beautiful 
colors:  yellow,  red,  green,  blue,  mostly  due  to  organic  matter, 
destroyed  by  ignition.  Pyroxene  (augite)  and  amphibole 
(hornblende)  are  generally  green  to  black,  from  iron  silicates. 
Quartz  and  calcite  show  also  most  of  the  colors  of  the  rainbow. 

8.  Contact  with  the  tongue  reveals  the  only  SOLUBLE 
mineral  in  the  list,  HALITE.  Hardness  2,  indentable  by  the 
finger  nail,  singles  out  gypsum  and  mica.  Of  these  two,  only 
GYPSUM  occurs  massive  and  fibrous;  when  foliaceous,  its 
folia  are  flexible,  but  not  elastic,  while  MICA  always  is  folia- 
ceous and  elastic  as  well  as  flexible.  [CRYOLITE  from 
Greenland,  has  greater  gravity  (3)  and  is  insoluble  in  water; 
otherwise  it  might  be  mistaken  by  hardness  and  cleavage  for 
poor  specimens  of  rock  salt.  See  p.  51.] 


114 


LECTURE  11. 


9.  Copper  hardness  (3)  gives  the  three  species  Calcite, 
Barite  and  ARAGONITE  (p.  67,  fig.  55).  This  latter  is  very 
rare,  almost  destitute  of  cleavage,  while  the  other  two  possess 
perfect  cleavages.  BARITE  is  readily  distinguished  by  its  high 
gravity,  which  has  given  it  the  common  name  Heavy  Spar. 
By  cleavage  it  yields  right  rhombic  tablets  of  101.7  degs. 
The  lighter  is  CALCITE  or  calcareous  spar,  the  most  common 
of  all  minerals,  which  will  receive  special  study  further  on. 
It  effervesces  with  vinegar. 

10.  FLUORITE  (Fluorspar)  and  APATITE  (p.  67,  fig.  37) 
are  not  scratched  by  copper.  Fluorite  generally  shows  its 
cleavages  readily,  while  apatite  practically  has  no  cleavage. 
The  four  cleavages  of  Fluorite  equally  developed  yield  a tetra- 
hedron (p.  66,  fig.  16) ; splitting  off  the  corners  also,  the 
regular  octahedron  (fig.  9)  results.  Fluorspar  crystallizes 
beautifully  (figs.  1,  5,  7,  14,  etc.)  and  shows  many  fine  colors; 
it  is  the  ERZBLUME  (ore  blossom)  of  the  old  miners,  ac- 
companying valuable  ores. 

11.  The  silicate  stones  are  easily  distinguished  by  hard- 
ness and  cleavage  combined.  One  eminent  cleavage,  MICA 
(isinglass)  ; no  cleavage,  QUARTZ,  if  hardness  7 (good  file). 
Hardness  below  this,  but  the  specimen  scratching  glass  quite 
readily,  showing  two  cleavages  under  a right  angle:  FELD- 
SPAR (p.  64:  Orthoclase  and  Anorthite,  here  called  Lepolith) 
which  is  reddish  or  whiteish,  except  in  the  bright  green 
Amazone  stone.  AUGITE  (Pyroxene,  p.  63)  and  HORN- 
BLENDE are  not  as  hard,  but  heavier,  blackish  and  greenish 
colors  prevailing;  only  if  showing  cleavage,  can  they  be  dis- 
tinguished, except  that  fibrous  varieties  are  hornblende. 

12.  Calcite  (p.  65)  exhibits  a thousand  modifications 
(secondary  forms)  of  its  rhombohedron,  P,  of  105.1  degrees, 
according  to  which  all  are  broken  up  by  the  cleavage  planes 
parallel  to  the  three  faces  of  the  rhombohedron  meeting  in  one 
corner  (HAUY,  p.  55).  The  most  common  secondary  forms 
are  the  Scalenohedra  (r,  figs.  15  to  21,  Dogtooth  Spar) ; next 
thereto  the  hexagonal  prism,  c,  and  the  obtuse  rhombohedron. 


CRYSTAL  STONES. 


115 


g (Nailhead  Spar).  Marble  is  crystalline  (saccharine  marble)  ; 
variegated  marble  may  be  massive.  Limestone  is  the  most 
common  form.  The  most  perfectly  transparent  cleavage 
pieces  come  from  Iceland  (Iceland  Spar)  ; next  in  perfection 
are  the  spars  from  Lampasas,  Texas. 


12.  ROCKS  AND  VEINS. 

1.  Limestone  generally  is  stratified,  forming  banks  or 
strata  of  varying  thickness,  apparently  deposited  in  a primeval 
sea.  The  strata  have  since,  in  many  places,  been  tilted  and 
broken.  Extensive  deposits  of  limestone  occur,  hundreds  of 
feet  in  thickness,  and  for  hundreds  of  miles  in  extent.  They 
furnish  locally  fine  building  stone  and  material  for  burning 
lime. 

2.  Many  LIMESTONES  are  quite  hard,  some  even  crystal- 
line; but  ah  effervesce  readily  with  vinegar.  The  beautiful 
white  MARBLE  of  Carrara  has  been  quarried  for  statuary  and 
ornamental  work  since  the  days  of  the  Romans,  (p.  51).  The 
Greeks  obtained  a superior,  more  fine  grained  marble  for  their 
statuary  and  monumental  buildings  from  the  island  of  Paros. 
Gypsum  also  forms  valuable  rock  deposits;  easily  dis- 
tinguished by  yielding  to  the  finger  nail  and  not  effervescing 
with  vinegar. 

3.  SANDSTONES  consist  of  grains  of  sand  (irregular  frag- 
ments of  quartz)  held  together  by  some  stony  cement,  often 
calcareous  and  effervescing  with  vinegar.  These  stones  are 
also  stratified,  but  less  extended  than  the  limestones;  they 
vary  exceedingly  in  their  characters,  as  to  color,  grain  and 
durability  of  the  cement.  Many  localities  offer  excellent 
building  stones  (Strasburg  Munster).  The  building  stones 
quarried  in  the  United  States  during  1895  had  a value  of  35 
million  dollars. 

4.  CLAY  like  deposits  form  extended  strata,  differing  in 
consistency  from  moist,  plastic  clays  to  shales  and  slates  (for 


116 


LECTURE  12. 


roofing).  When  heated  to  redness,  clays  lose  their  water, 
shrink  and  become  hard  (brick,  pottery.)  In  a bright  white- 
heat  most  ordinary  clays  will  show  signs  of  fusion ; the  purest 
clays  (white,  free  from  iron,  lime,  etc.)  resist  furnace  heat,  are 
called  fire  clay,  and  serve  for  crucibles,  finer  pottery,  to  porce- 
lain. All  these  clay  rocks  contain  aluminium  for  they  will 
(after  removing  iron,  etc.)  give  the  blue  cobalt  reaction  (7.9). 

5.  These  common  stratified  rocks — limestones,  sandstones 
and  shales — are  resting  upon  and  at  times  tilted  up  by  the 
the  two  principal  crystalline  siliceous  rocks,  the  graystones 
(granites)  and  the  GREENSTONES  (hornblendic  and  basaltic 
rocks).  In  granite  the  three  constituent  minerals  (mica, 
feldspar  and  quartz)  may  be  distinguished  without  much  diffi- 
culty. The  greenstones  are  heavier,  containing  more  iron. 

6.  During  great  convulsions,  the  rocks,  whether  stratified 
or  not,  have  been  cracked,  deep  fissures  running  nearly  paral- 
lel have  been  made.  In  the  course  of  time,  nature  has  healed 
these  wounds,  filled  up  these  crevasses  in  various  ways,  by 
materials  drawn  from  the  adjacent  rocks  (the  country)  or  from 
the  depths.  Such  filled  up  deep  crevasses  are  called  veins 
(p.  47),  especially  if  they  contain  ores  with  the  other  minerals 
or  veinstones  (gangue). 

7.  The  true  veins  extend  indefinitely  downwards;  their 
direction  on  the  ground  is  called  their  strike,  their  inclination, 
dip.  The  most  common  veinstones  are  quartz,  calcite,  fluorite 
and  barite.  These  gangues,  as  well  as  the  associated  ores, 
are  often  quite  symmetrically  distributed  across  the  vein,  that 
is,  if  from  the  left  the  order  of  minerals  be  a,  b,  c,  d,  it  will 
be  the  same  from  the  right  side  of  vein.  See  p.  47. 

8.  If,  after  a set  of. veins  has  formed,  like  convulsions  take 
place  again,  another  set  of  cracks  may  result,  leading  to  an- 
other set  of  veins  with  other  gangue  and  other  ores,  CROSS- 
ING the  first  and  older  ones,  which  thereby  may  have  been 
greatly  displaced.  (See  right  side,  p.  47).  At  Ehrenfried- 
ersdorf,  a set  of  silver  veins  run  from  north  to  south,  while  the 
tin  veins  run  from  east  to*  west. 


ROCKS  AND  VEINS. 


117 


9.  The  discovery  of  rich  veins  in  a new  country  is  a matter 
of  luck.  The  crowd  drawn  by  the  story  makes  a careful  and 
extended  search  (prospecting)  and  is  followed  by  the  general 
settler.  In  a few  years,  the  treasure  found,  has  added  a rich 
and  populous  state  to  civilization.  The  words  California, 
Colorado,  Australia,  Transvaal,  all  tell  the  same  story.  In 
Antiquity,  similar  effects  of  mining  are  recorded. 

10.  One  of  the  most  remarkable  stratified  rocks  is  stone 
coal,  H 2,  G 1.5  and  less,  black  combustible  (p.  48).  Anthra- 
cite (hard  coal)  gives  no  volatile  matter  (bitumen)  when 
heated  in  a tube;  the  other  coals  give  up  to  50  per  cent, 
bitumen,  and  burn  with  a luminous  flame.  Asphaltum  and 
Petroleum  are  essentially  natural  bitumens,  with  but  little 
fixed  carbon.  Stone  coal  supplies  our  industries  with  heat 
and  power;  largely  replacing  the  slave  labor  of  earlier  civiliza- 
tions. The  United  States  produced  265  million  dollars  worth 
of  mineral  combustibles  in  1895 — as  much  as  their  total  pro- 
duction of  metals. 

11.  Iron  ores  also  occur  as  rock  deposits.  The  magnetite 
(p.  52)  and  hematite  deposits  of  Elba  formed  the  center  of 
metallurgy  of  Antiquity.  We  have'  corresponding  deposits  in 
Missouri  (Iron  Mountain,  Pilot  Knob)  and  especially  on  Lake 
Superior  (Marquette  Region).  In  parts  of  England,  iron  ore, 
coal  and  flux  occur  in  neighboring  strata,  greatly  favoring  the 
smelting  of  the  iron. 

12.  Salt  is  obtained  by  the  evaporation  of  sea  water 
(France,  p.  50,  top)  ; from  salt  springs  (Michigan,  New  York)  ; 
and  above  all  as  rock-salt.  The  Stassfurth  rock-salt  deposit 
is  over  three  thousand  feet  thick.  That  at  Vilisca — over  one 
thousand  feet  thick— has  been  mined  for  centuries.  At  Cor- 
donna,  Spain  (p.  50),  rock-salt  is  q.uarried  from  a deposit 
reaching  over  five  hundred  feet  above  ground.  These  deposits 
are  aijsociated  with  gypsum  and  other  salts  of  sea  water, 
proving  them  to  be  the  result  of  evaporation  of  bays  of  a 
primeval  ocean,  or  inland  lakes  (Dead  Sea,  Great  Salt  Lake). 


13.  SALTS  AND  SPIRITS. 


1.  The  ancients  distinguished  a number  of  substances  re- 
sembling rock-salt  in  appearance,  solubility,  and  marked  by 
some  peculiar  taste ; the  term  SALT  has  been  used  to  designate 
all  materials  of  this  kind.  The  most  important  salts  have 
been  in  use  for  two  thousand  years ; surely,  every  student  of 
chemistry  should  be  able  to  recognize  them. 

2.  Already  the  Hebrews  used  two  very  soluble  salts  effer- 
vescing with  vinegar.  Neter  (to  effervesce)  was  found  in 
lakes  of  northern  Africa,  and  is  permanent  in  air;  we  call  it 
SODA.  The  other,  borith,  was  obtained  by  lixiviating  wood 
ashes;  it  is  our  very  deliquescent  POTASH.  Both  of  these 
substances  are  non  volatile  or  fixed.  A very  volatile  salt  of 
this  kind  (spiritus  urinse)  was  at  an  early  day  obtained  from 
putrid  urine;  we  call  it  Ammonium  Carbonate,  and  obtain  it 
from  stone  coal  (gas  works  refuse,  tar  water). 

3.  ALUM  is  a styptic  salt.  When  heated  in  a tube  it  gives 
off  much  water  and  leaves  a light,  white,  ash -like  residue, 
called  burnt  alum.  Accordingly,  the  ancients  said  alum  con- 
sists of  water  and  earth.  The  old  VITRIOLS  (glass-like)  are 
similar  salts,  styptic,  but  heavier  and  yielding  much  less  water; 
the  one  is  pale  GREEN  and  gives  iron  before  the  blowpipe, 
while  the  other  is  deep  BLUE  and  yields  copper..  Pyrites 
weathering  give  green  vitriol,  while  blue  vitriol  results  from 
the  weathering  of  copper  pyrites  (9.  8). 

4.  Our  nitre  or  SALTPETRE  (sal  petr«)  was  found  as 
crusts  on  rocks  in  caves  of  Asia  Minor;  it  is  distinguished 
from  the  preceding  salts  by  violently  deflagrating  on  glowing 
charcoal,  showing  its  leading  character  of  supporting  combus- 
tion. BORAX  on  the  contrary,  melts  quietly  to  a colorless 
drop  or  bead;  it  readily  dissolves  metallic  ashes,  forming 
characteristic  colors  therewith.  It  is  also  a most  useful  flux 
in  smelting. 


SALTS  AND  SPIRITS. 


119 


5.  Limestone  when  burnt  leaves  quick  LIME,  which  heats 
up  greatly  with  water;  yielding  slacked  lime  which  is  slightly 
soluble  in  water  (Limewater)  and  very  CAUSTIC  (corrosive 
to  the  skin  and  organic  tissue).  While  limestones  effervesce 
with  vinegar,  slacked  lime  does  not.  Concentrated  solutions 
of  the  effervescent  soluble  salts  (2)  yield  with  slacked  lime, 
upon  decantation,  the  most  caustic  liquids  known,  the  CAUS- 
TIC ALKALIES. 

6.  Sal  ammoniac  first  came  from  Egypt  in  fibrous  cakes., 
already  described  by  Dioscorides;  the  crude  salt  of  to-day 
has  the  same  characteristic  fibrous  structure.  When  warmed 
with  slacked  lime,  pungent  spirits  of  ammonia  are  abundantly 
produced  and  readily  taken  up  by  water,  giving  our  Aqua 
Ammoniae,  the  volatile  alkali. 

7.  The  ancient  chemists  studied  the  properties  of  all  ma- 
terials at  high  temperatures.  They  distinguished  the  very 
volatile  substances  as  we  do.  The  volatile  principle  collected 
in  a distilling  apparatus  they  termed  SPIRIT,  independent  of 
the  special  property,  which  might  be  acid,  like  vinegar,  neutral, 
like  water,  or  alkaline,  like  ammonia.  Litmus  turns  red  with 
acids,  blue  with  alkalies,  and  remains  unchanged  (blue  or 
red)  with  neutral  substances. 

8.  VINEGAR  (acetum)  is  the  only  acid  known  to  the 
ancients;  it  resulted  from  light  wines  exposed  to  air,  turning 
sour  (vin  aigre,  french).  We  have  used  it  to  recognize  lime- 
stone, marble,  soda,  by  the  effervescence  it  produces.  Vine- 
gar dissolves  lead,  yielding  SUGAR  OF  LEAD,  readily  soluble 
in  water.  Such  a solution  gives  an  abundant  white  precipi- 
tate with  vitriol  and  alum  solutions,  even  when  much  extra 
vinegar  has  been  added.  None  of  the  other  salts  show  this 
behaviour  ( reaction ) . 

9.  Alum  mixed  with  nitre  and  heated  gives  the  strongly 
acid  SPIRITS  OF  NITRE,  our  nitric  acid — the  “first  water”  of 
the  alchemists.  This  corrosive  liquid  stains  the  skin  and 
wood  yellow,  and  dissolves  copper  readily,  while  abundant  and 


120 


LECTURE  13. 


» very  noxious  red  fumes  (rutilant  vapors)  pass  off.  Silver 
also  dissolves  in  this  acid,  leaving  white  transparent  crystals — 
lunar  caustic,  lapis  infernalis — our  SILVER  NITRATE. 

10.  Alum  and  salt  (murias)  heated  in  the  same  manner 
yield  the  less  corrosive  SPIRITS  OF  SALT,  our  muriatic  acid. 
It  is  easily  distinguished  from  the  preceding  acids  by  giving  a 
white,  curdy  precipitate  with  silver  nitrate;  which  precipitate 
is  readily  dissolved  by  aqua  ammonia.  Accordingly,  silver  is 
insoluble  in  muriatic  acid. 

11.  Mixing  both  salt  and  nitre  with  alum,  heat  drives  off 
the  most  corrosive  acid,  AQUA  REGIA,  so  called  because  it 
dissolves  even  gold,  the  king  of  metals.  These  acids  were 
quite  generally  used  by  chemists  in  the  days  of  Geber,  more 
than  a thousand  years  ago.  Aqua  regia  was  called  the  “second 
water”  by  the  later  alchemists. 

12.  Intensely  heating  alum  (or  any  vitriol)  alone  (or  with 
dried,  pure  clay)  we  obtain  SPIRITS  OF  VITRIOL,  oui  sulphuric 
acid,  or  oil  of  vitriol.  It  chars  most  organic  materials  (wood), 
and  gives  the  same  white  precipitate  with  sugar  of  lead  which 
we‘  obtained  with  alum  and  vitriol  solutions. 

At  present,  the  term  spirit  is  restricted  to  the  distillate  from 
wine  and  similar  liquids;  our  alcohol  is  spirits  of  wine,  spiritus 
vini. 


Notes.  Section  ii  is  in  accordance  with  current  information,  accept- 
ing the  works  of  Geber  as  they  exist  in  latin  to  be  genuine,  due  to  the 
arab  Djaber  (eighth  century).  But  Berthelot  has  published  the  original 
text  in  arabic  and  finds  (Comptes  Rendus,  T.  ii6,  p.  1 166-1171;  1S93) 
that  the  latin  works  accepted  for  centuries  as  the  translation  thereof,  are 
works  of  European  chemists  of  much  later  date;  that  the  arabs  did  not 
add  to  the  chemistry  of  the  Greek  school.  Consequently,  that  “ thous- 
and years  ago  ” will  have  to  be  cut  in  two,  leaving  say  half  a thousand 
years. 


14.  SOLUTION  AND  CRYSTALLIZATION. 


1.  THE  OCEAN  is  the  greatest  residual  solution  on  the 
globe.  The  taste  of  its  water  reveals  the  presence  of  common 
and  bitter  salts.  By  evaporation  sea-salt  is  obtained  there- 
from. The  great  (rock)  salt  deposits  have  undoubtedly  been 
formed  in  bays  periodically  in  narrow  communication  with  the 
ocean  (12,  12;  Atlas,  p.  50).  Seawater  contains  3j  percent, 
of  salts,  varying  slightly  in  different  regions.  Forchhammer^ 
1864. 

2.  SOLUTION  is  the  conversion  of  a solid  into  a liquid  by 
means  of  a liquid.  The  liquid  used  is  called  the  solvent,  the 
liquid  resulting  is  called  the  solution.  The  word  solution  thus 
is  used  both  for  the  operation  and  the  result.  A solution  is 
saturated,  when  in  contact  (aided  by  repeated  shaking)  with 
the  finely  pulverized  solid,  it  does  not  take  up  any  more 
thereof.  Concentrated  is  a solution  approximating  saturation; 
dilute  when  remote  from  it.  Water  is  the  most  common  sol- 
vent; alcohol,  ether,  and  other  volatile  liquids  are  also  used. 

3.  THE  SOLUBILITY  of  a solid  is  the  weight  thereof  dis- 
solved to  a saturated  solution  by  a unit  of  weight  of  solvent 
(Gay-Lussac,  1819).  It  may  also  be  defined  as  the  weight 
of  the  solid  contained  in  a unit  of  weight  of  the  saturated  so- 
lution (Etard,  1894).  For  practical  purposes,  the  STRENGTH 
OF  ANY  SOLUTION  (whether  saturated  or  not)  is  usually 
given  by  stating  the  weight  of  solid  per  unit  of  volume  of  the 
solution;  that  is  in  milligrammes  per  cubic  centimeter  or 
grammes  per  Liter. 

4.  THE  SOLUBILITY  INCREASES  WITH  THE  TEMPERA- 
TURE, as  shown  by  the  diagrams,  p.  70.  For  alum,  nitre 
and  blue  vitriol  dissolved  in  water,  the  increase  is  very  rapid, 
the  Gay-Lussac  curves  rising  steeply.  Salt  shows  but  a very 
slight  change  in  solubility.  The  Etard  lines,  p.  71,  are 
straight,  or  consist  of  several  straight  lines,  the  last  section 


122 


LECTURE  14. 


(except  for  sulphates)  running  to  the  melting  point.  All 
chemistry  in  the  WET  WAY  is  but  an  application  of  the  facts 
of  solubility. 

5.  When  a given  solid  is  divided,  the  surface  increases 
rapidly,  while  the  weight  remains  unchanged.  As  solution 
can  only  take  place  at  the  surface  of  the  solid  in  contact  with 
the  solvent,  it  follows  that  PULVERIZATION  must  greatly 
accelerate  solution.  Solids  are  first  broken  with  hammer  and 
anvil,  then  crushed  in  a diamond  mortar  (steel  socket  with 
steel  pestle),  and  finally  ground  thoroughly  fine  in  appropriate 
mortars  (porcelain,  agate). 

6.  WARMING  the  finely  pulverized  solid  with  a reasonable 
excess  of  solvent  will  effect  rapid  solution  of  all  that  is  soluble. 
Any  insoluble  impurities  will  remain  in  the  solid  state.  They 
can  be  removed  by  DECANTATION  after  the  solution  has  been 
standing  undisturbed  to  permit  the  solids  to  settle;  or  better 
and  more  rapidly,  they  are  removed  by  FILTRATION  through 
a porous  insoluble  solid,  usually  filter  paper,  supported  in  a 
funnel  of  60  degrees  aperture. 

7.  A hot,  concentrated  solution  set  aside  will  COOL  slowly, 
and  generally  soon  show  the  growth  of  beautiful  CRYSTALS, 
the  solubility  diminishing  as  the  temperature  sinks.  With  an 
almost  boiling  saturated  solution  of  nitre,  a half  dozen  con- 
secutive crops  of  bulky  masses  of  silky  crystals  may  be  ob- 
tained by  as  many  consecutive  decantations,  showing  most 
strikingly  the  enormous  decrease  of  solubility  of  nitre  upon 
cooling. 

8.  While  the  gradual  cooling  of  a hot,  concentrated  solu- 
tion gives  rapidly  large  groups  of  crystals,  the  most  perfect 
crystals  are  generally  obtained  from  saturated  solutions  by 
SPONTANEOUS  EVAPORATION,  in  crystallizing  basins  and 
dishes  of  glass  or  porcelain.  On  a small  scale,  watch  glasses 
answer  admirably.  For  work  with  the  magnifier  and  the 
MICROSCOPE,  a drop  of  solution  on  the  microscope  slide  is 
-sufficient.  Creeping  is  avoided  by  a line  drawn  with  paraffin. 


SOLUTION  AND  CRYSTALLIZATION. 


123 


9.  By  careful  work  a COLLECTION  OF  CRYSTALS  of  the 
more  common  substances  may  thus  be  obtained.  The  best 
crystals  are  comparatively  small,  and  require  a magnifier  for 
close  study.  A trifle  of  wax,  rolled  on  the  head  of  a pin,  serves 
to  support  the  crystal.  The  pin  stuck  into  the  cork  of  a speci- 
men tube  mounts  and  protects  the  crystal  quite  nicely.  A 
paper  strip  as  wide  as  the  cork  is  long,  around  the  tube,  forms 
the  proper  label. 

10.  The  study  of  this  subject  is  very  much  facilitated  by 
procuring  at  drug  stores  a few  LARGER  CRYSTALS  that  can  be 
picked  out  from  a drawerful  of  blue  vitriol,  alum,  nitre,  yellow 
prussiate  of  potash,  potassium  sulphate,  and  the  like.  Rock- 
candy,  in  large  crystal  groups  on  strings,  is  also  obtainable  at 
candy  stores.  A few  native  crystals  from  dealers  in  minerals 
will  greatly  add  to  the  value  of  the  collection. 

11.  The  operations  of  solution,  filtration  and  crystallization 
are  employed  not  only  in  the  laboratory,  but  in  chemical  works 
to  obtain  pure  products  from  impure  raw  materials  (REFINING). 
Many  of  these  raw  materials  are  transported  from  hot  or  desert 
regions  to  Europe  and  the  United  States  to  be  refined;  salt- 
peter from  India,  borax  from  the  dead  valley  of  Arizona  (for- 
merly from  Thibet  to  Venice),  Chili  saltpeter  from  South 
America,  raw  sugar  from  the  tropics.  Alum  and  blue  vitriol 
works  are  among  the  oldest  establishments  producing  pure 
•chemicals. 

12.  Most  soluble  substances  are  associated  not  only  with 
insoluble  materials  removable  by  filtration,  but  also  with 
substances  merely  differing  in  solubility.  The  less  soluble 
will  crystallize  first,  the  most  soluble  last;  so  that  by  setting 
.aside  of  the  first  crop  of  crystals,  and  decanting  before  the 
substance  wanted  is  all  deposited,  very  pure  materials  are  ob- 
tained. This  process  of  FRACTIONAL  CRYSTALLIZATION  is 
one  of  the  most  simple  and  effective  means  for  obtaining  pure 
chemical  individual  substances. 


15.  CRYSTAL  DESCRIPTION. 


1.  Magnificent  specimens  of  CRYSTALS  are  found  IN' 
MINERALOGICAL  MUSEUMS— and  beautiful,  though  smaller, 
crystals  of  the  most  varied  kind  are  MADE  IN  THE  LABO- 
RATORIES. But  their  forms  seem  bewildering;  no  two  crystals; 
of  the  same  substance  appear  to  be  exactly  alike. 

2.  The  ancients  were  familiar  with  the  large  quartz  crystals- 
of  the  Alps  and  the  splendid  blue  vitriol  crystals  made  in 
Spain.  Pliny  speaks  of  both;  the  former  he  considers  ice 
(KRYSTALLOS,  in  Greek)  so  hard  frozen  that  heat  cannot 
thaw  it  (Hist.  Nat.  37,  9),  the  latter  he  believes  to  be  a glass 
vitrum,  hence  our  word  vitriol  (Hist.  Nat.  34,  11).  It  is  only 
in  modern  days  that  the  characteristic,  fixed  features  in  this 
form  of  crystals  have  been  discovered.  Accordingly  we  now 
can  describe  a crystal  in  such  a way  that  its  form  can  be 
identified  and  recognized  by  that  description. 

3.  The  Dane  STEEN  (or  Steno)  discovered  (1669  in  Italy) 
that  while  the  linear  dimensions  of  the  six-sided  quartz  crys- 
tals varied  infinitely  (see  p.  65)  the  angles  between  adjacent 
faces  of  that  prism  (rr)  are  constant,  always  exactly  120 
degrees.  Crystallographically,  as  to  these  INTER-FACIAL 
ANGLES,  the  quartz  prism  therefore  is  a REGULAR  hexagon 
of  120  degrees.  ROME  DE  LTSLE  (p.  54)  and  especially 
HAUY  (p.  55)  have  laid  the  foundation  of  crystallography 
upon  this  law  of  Steno. 

4.  A CRYSTAL  IS  A POLYHEDRON  FORMED  SPON- 
TANEOUSLY. This  is  the  best  and  most  simple  definition 
that  can  be  given.  Its  expresses  the  two  fundamental  facts, 
that  crystals  are  bounded  by  plane  surfaces  called  faces,  and 
form  without  external  influences,  the  substance  being  left  en- 
tirely to  itself.  The  line  of  intersection  of  two  faces  is  called 
an  EDGE.  The  point  where  three  or  more  faces  meet  is- 
called  a CORNER. 


CRYSTAL  DESCRIPTION. 


125 


5.  Three  or  more  faces  having  their  edges  parallel  consti- 
tute a ZONE  or  PRISM.  This  prism  is  limited  or  cut  off  by 
■one  or  more  faces.  If  one  face,  it  is  called  the  BASE— right  if 
at  right  angles  to  the.  edges,  oblique  if  not.  If  the  prism  is 
cut  off  by  two  faces  under  an  angle,  as  the  roof  on  a house, 
these  faces  are  called  a DOME,  also  right  or  inclined,  accord- 
ing as  the  ridge  is  perpendicular  or  not  to  the  edges  of  the 
prism.  If  limited  by  three  or  more  faces,  the  prism  is  said  to 
be  surmounted  by  PYRAMID. 

6.  The  general  appearance  of  a crystal  is  distinguished  as 
TABULAR  or  PRISMATIC,  according  as  two  dimensions  or  one 
only  predominates.  If  a corner  or  edge  is  replaced  by  a face, 
it  is  said  to  be  TRUNCATED.  If  an  edge  is  replaced  by  two 
faces,  it  is  BEVELLED.  The  general  predominance  of  a par- 
ticular set  of  forms  is  called  the  HABITUS,  and  depends  on  the 
special  conditions  under  which  the  crystals  grew.  See  10,  9. 

7.  The  interfacial  angle  of  »a  crystal  can  be  determined  . 
with  sufficient  accuracy  for  all  purposes  of  identification  by  my 
diagram  GONIOMETER  (p.  68)  for  student’s  use.  Hold  the 
edge  of  the  crystal  so  that  it  appears  as  a point,  and  the  two 
faces  as  lines — then  the  edge  will  be  vertical  to  the  paper 
goniometer,  and  it  will  be  easy  to  find  the  angle  most  nearly 
identic  with  the  interfacial  angle  concerned. 

8.  The  crystal  is  held  mounted  on  a pin  or  by  means  of 
forceps,  and  the  eye  may,  for  small  crystals,  be  assisted  by  a 
magnifying  glass  of  low  power,  that  is,  if  long  focus.  Both 
large  and  small  crystals  are  readily  measured  in  this  manner. 
After  some  practice,  the  nearest  degree  can  be  ascertained, 
though  in  description  the  TENTH  of  a degree  will  be  stated 
for  reference.  Thus  calcite  is  about  105  degrees;  exactly 
105.1  degrees. 

9.  BLUE  VITRIOL  (p.  68)  crystals  show  the  dominant 
zones  MT  123.2,  PT  127.7  and  MP  109.2.  In  the  first  zone 
the  faces  n,  I,  r replace  edges,  so  that  Tr  110.2,  Tn  148.8, 

Mr  126.7.  Also  Pn  120.8  and  Pr  103.4. 


126 


LECTURE  15. 


Special  characters:  Crystals  tabular  after  M;  face  T looks 
rectangular;  face  N is  frequently  striated  parallel  to  edge  MT ; 
and  face  P in  coarse  crystals  shows  curved  projections  due  to 
disturbed  rapid  growth.  These  forms  are  evidently  triclinic, 
destitute  of  symmetry;  10,  3,  note. 

10.  Nitre  (p.  68)  forms  right  prisms,  M M'b,  very  nearly 
hexagonal;  MM'  119.4,  Mb  120.3.  The  right  dome  D meas- 
ures 109.8  and  Db  125.1.  Crystals  often  tabular  after  b. 
ALUM  is  octahedral  (O)  with  corners  (hexahedron,  H)  and 
edges  (dodecahedron,  D)  truncated.  OO  109.5,  OH  125.3, 
OD  144.7,  and  HH  90.0,  DD  120.0  Crystals  commonly  grow 
resting  on  a face  of  the  octahedron,  and  thus  show  rhombo- 
hedral  appearance,  the  three  D forming  a rhombohedron  of 
120  and  the  three  H one  of  90  degrees. 

11.  THE  FERROUS  SALT  (hydrated  ammonio-ferrous 
sulphate)  forms  tabular  crystals,  the  oblique  base  P dominat- 
ing and  striated.  The  prism  MM'  about  109,  and  MP=M'P 
about  105  degrees.  The  characteristic  triangular  truncatures 
q form  Pq  about  155  degrees. 

These  crystals  form  very  readily  by  mixing  strong. solutions 
of  ammonium  sulphate  and  of  ferrous  sulphate  (green  vitriol) ; 
even  a drop  each  on  the  microscope  slide  will  suffice.  This 
double  salt  is  permanent  in  air;  green  vitriol  is  not. 

12.  The  ferrous  (pale  green)  solution  may  be  replaced  by 
nickel  (deep  green),  cobalt  (pink),  manganese  (pale  rose), 
copper  (deep  blue),  or  the  colorless  solution  of  magnesium, 
zinc  or  cadmium  sulphates.  In  all  cases,  these  solutions  will, 
with  ammonium  sulphate  solution,  give  crystals  of  the  same 
general  form  and  nearly  the  same  angles;  such  compounds  are 
called  ISOMORPHOUS.  The  habitus  may  be  more  prismatic 
or  more  tabular,  according  as  MM'  or  P dominates.  Isomor- 
phism was  discovered  by  ElLHARD  MlTSCHERLlCH  (1794- 
1863) ; portrait  p.  34. 


16.  MARBLE  AND  FIXED  AIR. 

1.  CALCITE  in  all  its  natural  varieties,  down  to  the  common 
limestone,  has  the  property  of  promptly  effervescing  with  vine- 
gar; a drop  of  vinegar  placed  on  the  specimen  produces  the  ap- 
parent boiling  up  (11,9).  In  a test  tube  this  shows  better;  in 
large  cylinders  and  flask  the  phenomenon  becomes  very  strik- 
ing. It  is  also  advisable  to  take  a common  mineral  acid,  like 
muriatic  or  nitric  acid  instead  of  vinegar.  Sulphuric  acid 
cannot  be  used,  giving  a precipitate  with  lime  solution. 

2.  TO  STUDY  THE  GAS  set  free  in  this  effervescence,  it  is 
necessary  to  produce  it  in  quantity  and  to  collect  it.  The 
most  convenient  generator  is  Kipp’s,  because  it  will  yield  the 
gas  exactly  as  it  is  required.  The  upper  compartment  is 
charged  with  clean  fragments  of  marble  as  large  as  can  be  in- 
troduced through  the  tubulature.  The  acid  is  dilute  muriatic, 
3 water  to  1 acid.  We  remove  the  lower  glass  stopper,  re- 
place it  by  a rubber  stopper  (well  tied  or  wired)  connected 
with  rubber  tube,  as  shown.  Then  the  pressure  can  be 
promptly  released  at  the  close  of  the  working  hours. 

3.  THE  GAS  is  drawn  by  slightly  turning  the  delivery 
stopcock.  It  may  be  collected  in  cylinders  over  the  pneu- 
matic trough  or  in  empty  gas  washing  bottles;  best  the 
Drechsler  form  made  entirely  of  glass.  A series  of  such 
cylindrical  washing  bottles  may  be  connected  by  rubber  tubes 
and  thus  the  different  reactions  of  the  gas  shown  at  one 
view.  These  cylindrical  bottles  are  easily  detached  by  the 
ground  joint,  so  that  the  reagents  can  be  introduced  at  any 
time. 

4.  COLOR,  ODOR,  TESTS.  The  gas  collected  over  the 
water  or  in  the  washing  cylinders  cannot  be  distinguished  by 
sight  from  the  air  surrounding  the  apparatus — it  is  colorless. 
Nor  has  the  escaping  gas  been  recognized  by  odor — it  is  odor- 
less. In  a wash  bottle  containing  blue  litmus,  a wine  red  tint 


128 


LECTURE  16. 


is  produced  as  the  gas  passes  through— it  is  soluble  in  water, 
and  that  solution  is  an  acid.  In  another  cylinder,  lime  water 
becomes  turbid  (white  precipitate),  which  increases  in  amount, 
finally  diminishes  again,  and  dissolves. 

5.  This  solution,  exposed  to  the  air  in  a shallow  vessel, 
gradually  deposits  microscopic  rhombohedral  crystals,  exactly 
of  the  same  form  as  the  calcite  rhombohedron  of  105  degrees. 
They  effervesce  with  acids,  give  the  orange  tint  to  the  blow- 
pipe flame,  exactly  as  calcite;  they  are  ARTIFICIAL  CALCITE. 
They  show  beautiful  colors  in  the  polarizing  microscope. 

6.  THE  GAS  IS  decidedly  HEAVIER  THAN  atmospheric  AIR; 
for  it  can  be  poured  out  of  one  vessel  into  another,  exactly  like 
water.  A little  lime  water  in  the  lower  vessel  becomes  turbid, 
especially  after  shaking.  A burning  taper  at  the  bottom  of 
the  lower  cylinder  will  be  extinguished,  as  the  gas  is  poured 
into  that  cylinder — the  same  as  if  the  taper  were  lowered  into 
a vessel  filled  with  the  gas.  The  gas  does  NOT  SUPPORT 
COMBUSTION. 

7.  PROPERTIES.  The  gas  set  free  by  an  acid  acting  on 
calcite  thus  is  colorless,  odorless,  heavier  than  air,  does  not 
support  combustion;  it  is  soluble  in  water,  forming  an  acid, 
makes  lime  water  turbid,  an  excess  redissolves  the  precipitate, 
.and  from  that  solution  the  original  calcite  deposits  in  perfect 
rhombohedral  crystals.  This  gas  is  evidently  contained  (fixed) 
in  all  forms  of  calcite;  it  was  called  FIXED  AIR  by  Black  of 
Edinburgh  (1755),  who  first  most  thoroughly  studied  it. 

8.  This  gas  was  first  produced  by  VAN  HELMONT  (1577- 
1644),  who  introduced  the  term  GAS;  really  spirit,  ghost 
(engl.),  ghoast  (dutch),  geist  (german)-,  gast  (anglo-saxon). 
He  called  it  gas  sylvestre  (spiritus  sylvestris)  or  wild,  savage 
gas,  because  he  was  unable  to  tame  and  control  it,  so  as  to 
collect  and  handle  it.  (See  portrait,  p.  30).  Since  Black,  it 
has  been  called  carbonic  acid — but  the  dry  gas  itself  has  no 
acid  properties.  Then  it  was  called  carbonic  anhydride,  and 


MARBLE  AND  FIXED  AIR. 


129 


now  it  is  quite  learnedly  called  carbon  dioxide!  Bergman 
(1774)  called  it  acidum  aereum. 

9.  BURNING  CHARCOAL  in  a current  of  air,  the  product 
of  combustion  will  show  all  the  properties  of  fixed  air;  hence, 
fixed  air  contains  carbon.  In  this  experiment  the  charcoal  is 
heated  in  a tube  of  Bohemian  glass  connected  with  the 
Drechslers,  which  are  attached  to  an  aspirator,  producing  the 
current  of  air.  Air  exhaled  shows  like  properties;  so  does  air 
from  fermenting  grape  juice. 

10.  Fixed  air  has  been  LIQUEFIED  to  a limpid,  colorless 
liquid  by  cold  and  pressure  (Faraday,  1823);  but  no  amount 
of  pressure  will  liquefy  it  above  31  degrees.  That  is,  above 
31  degrees  it  is  a true,  non -liquefiable  gas;  below  31  degrees 
it  is  a condensable  vapor.  This  limiting  temperature  be- 
tween vapor  and  true  gas  is  called  the  CRITICAL  TEMPERA- 
TURE. The  pressure  sufficient  to  liquefy  it  at  that  temperature 
is  73  atmospheres.  At  — 78  degrees,  fixed  air  CRYSTALLIZES 
to  white,  snow-like  masses  (Thilorier,  1835). 

11.  LIQUID  FIXED  AIR  (liquid  carbonic  acid)  is  now  pro- 
duced in  chemical  works  and  sold  in  steel  cylinders  to  various 
industries.  The  solution  of  fixed  air  in  water,  made  strong  by 
using  from  2 to  5 atmospheres  pressure,  is  used  as  a refresh- 
ing beverage  (soda  water)  ; it  is  also  produced  in  the  portable 
fire-extinguishers  and  chemical  fire  engines.  Many  natural 
spring  waters  are  also  stron'gly  carbonated,  that  is,  impregnated 
with  fixed  air. 

12.  RAIN  DROPS  ABSORB  FIXED  AIR  while  falling,  and 
while  sinking  through  the  soil.  Reaching  the  rocks  below, 
the  water  will  slowly  dissolve  limestone,  become  hard — de- 
positing kettle  stone  when  boiled.  Such  rock-water,  reaching 
fissures  or  cavities,  will  lose  its  fixed  air  and  deposit  the  lime- 
stone it. held  in  solution  as  calcite,  often  finely  crystallized. 
Thus  chemical  changes  (METAMORPHOSES)  are  going  on  in 
the  depths  of  the  earth. 


17.  ZINC  AND  INFLAMMABLE  AIR. 


1.  Iron  is  insoluble  in  water;  iron  pipes  are  used  for 
water  conduits  in  cities.  But  if  to  the  water  standing  over 
scrap  iron,  oil  of  vitriol  be  gradually  added,  effervescence  will 
promptly  start  up;  an  inflammable  gas  of  unpleasant  odor 
will  escape  in  abundance.  Paracelsus  (1493-1541)  has  first 
described  this  quaintly:  Air  rises  and  bursts  forth  like  a 
wind.  BOYLE  (1626-1691)  first  collected  this  gas.  See 
portrait  p.  21. 

2.  Cavendish  (1731-1810)  first  carefully  studied  this  gas 
which  he  called  INFLAMMABLE  AIR.  He  found  it  colorless 
and  odorless  (when  pure);  the  lightest  of  all  gases  (1765); 
inflammable,  producing  water  when  burning.  With  air  it 
forms  an  explosive  mixture.  Hence,  great  care  is  required 
when  handling  this  gas  near  any  flame;  the  explosions  are 
violent,  so  much  so  that  Lemery  thought  (1675)  thunder 
due  to  the  “ fulminations  ” of  this  gas. 

3.  TO  GENERATE  INFLAMMABLE  AIR  in  quantity,  charge 
a Kipp  with  ordinary  granulated  zinc  and  dilute  muriatic  acid. 
Collect  a cylinder  full  (100  or  200  cc)  over  the  through,  and 
carry  the  filled  cylinder  to  a flame — the  gas  will  explode.  Let 
the  Kipp  be  emptied  a few  times,  filling  up  by  closing  the 
stop-cock.  Trying  another  cylinder  of  the  gas  now  collected, 
it  will  burn  quietly,  without  explosion ; this  is  a sign  that 
the  gas  is  free  from  air. 

4.  THE  EXTREME  LIGHTNESS  of  the  inflammable  air  is 
shown  by  holding  a cylinder  containing  air  for  a few  moments 
over  a cylinder  containing  the  gas,  and  now  trying  both  at  the 
flame,  the  gas  in  both  will  burn  with  explosion. 

Careful  determinations  have  shown  that  under  ordinary 
conditions  (of  temperature  and  pressure)  twelve  cubic  centime- 
ters of  inflammable  air  weigh  one  milligramme  (0.083  mgr. 
per  cc). 


ZINC  AND  INFLAMMABLE  AIR. 


m 


5.  The  gas  generated  from  zinc  has  not  as  unpleasant  an 
odor  as  that  generated  from  iron;  it  is  less  impure.  TO 
PURIFY  A GAS  it  must  pass  slowly  through  absorption  and 
washing  tubes,  containing  the  proper  absorbents.  If  these 
are  in  the  liquid  form,  it  requires  pressure  to  force  the  gas 
through;  hence,  it  is  generally  preferable  to  soak  fragments 
of  pumice  with  the  absorbent  liquids  and  pack  these  frag- 
ments in  cylinders. 

6.  The  most  effective  ABSORBENTS  for  purifying  inflam- 
mable air  are  lead  and  silver  solutions  (removing  the  odorous 
gases),  caustic  potash  solution  (removing  traces  of  acids)  and 
concentrated  oil  of  vitriol  one  of  the  most  effective  dryers, 
being  strongly  hygroscopic. 

7.  For  such  purposes  the  Drechslers  are  not  applicable. 
We  generally  use  cylinders  of  glass,  on  foot,  so  they  will 
stand  firmly,  and  provided  with  a tubulature  in  a lower 
division,  separated  from  the  main  upper  parts  by  a narrow 
contraction,  preventing  the  fragments  of  pumice  from  falling. 
Connection  is  made  by  rubber  stopper  and  glass  tubing  at  the 
top  opening  and  at  the  tubulature  below.  A number  of  such 
cylinders  are  used  in  series. 

8.  If  the  inflammable  air  is  carefully  dried  so  that  it  will 
pass  through  a tube  surrounded  with  fragments  of  ice  without 
depositing  moisture  in  the  same,  it  can  be  connected  with  a 
small  burner  (like  the  microchemical  burners)  and,  after  due 
precautions,  the  jet  may  be  lit.  IT  WILL  BURN  with  a pale, 
very  hot  flame.  A bell  glass  held  over  the  flame  will  bedew, 
and  WATER  will  soon  run  in  drops  down  into  a plate  placed  to 
receive  it. 

9.  Since  inflammable  gas  produces  or  generates  water 
(Greek:  hydor)  when  burning,  it  was  called  HYDROGEN  by 
Lavoisier  -(p.  19).  The  chemical  symbol  of  hydrogen  is  FI. 

Experience  has  shown  that  HYDROGEN  IS  CLOSELY  RE- 
LATED TO  THE  METALS,  several  of  which  form  genuine 
alloys  with  it.  Palladium  absorbs  a thousand  times  its  own 


132 


LECTURE  18. 


volume  of  hydrogen  (Graham)  ; it  is  used  in  gas  analysis  to 
remove  hydrogen  from  other  gases. 

10.  In  recent  days,  since  very  low  temperatures  have  been 
produced  on  a sufficiently  large  scale,  it  has  been  found 
(Olszewski,  1895)  that  the  CRITICAL  POINT  of  hydrogen 
gas  is  at  234.5  degrees  below  the  freezing  point,  and  that  the 
critical  pressure  is  20  atmospheres.  Below  this  temperature 
hydrogen  is  a vapor,  liquefiable  by  an  increase  of  pressure. 

11.  Any  of  the  acids  can  he  used  instead  of  muriatic,  es- 
pecially nitric,  sulphuric  and  even  acetic.  THE  METAL§ 
THAT  DISSOLVE  more  or  less  readily  IN  some  of  these 
DILUTE  ACIDS  are,  in  addition  to  iron  and  zinc:  Magnesium, 
aluminium,  cadmium,  nickel,  cobalt,  lead.  The  special  con- 
ditions of  solution  will  be  studied  in  due  season.  Lead  is 
insoluble  in  both  muriatic  and  sulphuric  acids. 

12.  In  many  cases,  especially  where  sulphuric  acid  has 
been  used,  CRYSTALS  FORM,  in  which  the  blowpipe  readily 
detects  the  metal  originally  dissolved.  Some  of  these  crys- 
tals, especially  the  sulphates,  contain  water  of  crystallization, 
easily  driven  off  by  heating  the  crystals  in  a glass  tube. 


18.  SUBSTITUTION  BY  SOLUTION. 

1.  THE  CONTRAST  between  the  solution  of  marble  and 
metals  in  ACIDS  and  salts  in  WATER  must  have  become 
apparent.  When  the  salt  dissolves  in  water  nothing  escapes, 
and  upon  evaporation,  the  original  salt  is  reproduced,  fre- 
quently in  crystals.  When  the  metals  dissolve  in  acid,  a 
gas  escapes,  a new  substance  forms,  no  longer  the  metal, 
but  containing  the  metal,  as  proved  by  means  of  the  blow-pipe. 

2.  Accordingly  we  have  two  different  kinds  of  solution, 
simple  and  CHEMICAL  SOLUTION,  also  distinguished  as  solu- 
tion and  dissolution.  The  first  is  largely  physical  in  its 
nature;  the  second  is  entirely  chemical,  the  original  sub- 


SUBSTITUTION  BY  SOLUTION. 


133 


stances  both  disappear  and  are  replaced  by  two  new  and 
totally  different  substances.  Thus  we  have  entered  the  very 
center  of  CHEMISTRY  IN  THE  WET  WAY. 

3.  In  the  solution  of  any  metal  in  a dilute  acid,  HYDRO- 
GEN GAS  is  always  produced.  The  solution  obtained  in 
many  cases — detailed  directions  belong  to  practical  chemistry 
— crystallizes,  in  all  cases  can  be  evaporated  to  dryness,  so 
that  the  new  salt  is  obtained  by  itself,  free  from  water  and 
any  excess  of  acid — the  last  best  avoided  by  having  an  excess 
of  metal,  and  decanting  the  solution.  IN  THE  SALT,  the 
blowpipe  readily  detects  THE  METAL  used  and  dissolved. 

4.  For  example,  in  the  preparation  of  hydrogen  gas  by 
means  of  zinc  and  dilute  sulphuric  acid,  we  obtain  the  gas 
and  a white  crystallized  salt  containing  zinc;  this  salt  is  iden- 
tical with  common  white  vitriol.  A solution  of  this  salt  gives 
an  abundant  white  precipitate  with  lead  acetate,  precisely  as 
does  the  acid  used;  it  contains,  therefore,  the  essential  or 
chemical  characteristic  part  of  sulphuric  acid.  Hence,  it  is 
termed  a sulphate,  namely  ZINC  SULPHATE. 

5.  The  chemical  solution  considered  may  now  be  repre- 
sented thus:  Zinc  and  sulphuric  acid  give  hydrogen  gas  and 
zinc  sulphate.  Evidently  the  hydrogen  must  have  formed 
part  of  the  sulphuric  acid.  It  is  known  to  be  metallic  in  its 
real  nature  (17.9).  We  have  here  apparently  an  exchange  of 
metals,  hydrogen  for  zinc;  consequently  the  acid  itself  must  be 
hydrogen  sulphate.  In  other  words,  the  ACID  IS  A HYDRO- 
GEN SALT,  exactly  as  white  vitriol  is  a zinc  salt,  the  salt  of 
a metal. 

G.  The  above  REACTION— that  is  chemical  action — be- 
tween the  metal  and  the  acid  may  therefore  be  written  as 
follows:  Zinc  and  hydrogen  sulphate  give  hydrogen  and 
zinc  sulphate.  Such  a reaction  in  which  any  substance  A 
takes  the  place  of  any  other  substance  B in  any  combina- 
tion, setting  free  this  second  B,  is  called  a SUBSTITUTION. 
The  above  reaction  is  the  substitution  of  zinc  for  the  hydrogen 
of  the  acid.  See  blackboard  diagram. 


134 


LECTURE  18. 


7.  Having  studied  the  qualitative  side  of  this  fundamental 
reaction,  we  must  next  try  to  determine  the  QUANTITATIVE 
RELATIONS  of  the  same.  The  merest  trials  show  that  with- 
out weighing  the  quantities  used,  there  either  remains  metal 
or  acid  in  excess.  To  obtain  the  best  salt  it  is  generally 
advisable  to  have  an  excess  of  the  metal,  decanting  the  liquid 
when  th^  reaction  ceases  and  setting  the  liquid  aside  to 
crystallize. 

8.  First,  TO  DETERMINE  THE  AMOUNT  OF  HYDROGEN 
GAS  the  latter  must  be  measured  in  a gas  burette.  The  evo- 
lution tube  is  charged  with  an  excess  of  the  acid  and  the 
accurately  weighed  metal— the  latter  held  on  the  slanting 
walls  of  the  dry,  inclined  tube  above  the  acid.  When  the 
burette  is  properly  adjusted,  the  operation  is  started  by  simply 
bringing  the  evolution  tube  to  a perpendicular. 

9.  MAGNESIUM  ribbon  is  specially  convenient  for  these 
determinations.  It  is  found  that  a cubic  centimeter  of  hydro- 
gen gas  is  produced  for  each  milligramme  of  magnesium  used, 
very  nearly.  As  12  cc  hydrogen  gas  weigh  one  milligramme 
(17.4)  THE  UNIT  OF  ONE  MILLIGRAMME  OF  HYDROGEN 
IS  EQUIVALENT  TO  TWELVE  MILLIGRAMMES  OF  MAGNE- 
SIUM. 

10.  Repeating  the  experiment  with  zinc  we  find  that  it 
requires  nearly  32  mgr.  of  zinc  to  give  12  cc  gas  representing 
1 mgr  gas,  at  the  same  time  (under  same  pressure  and  tem- 
perature). For  iron  the  equivalent  number  is  28.  For  alum- 
inium— easiest  dissolved  in  an  alkaline  liquid  (13.5) — the 
equivalent  is  found  to  be  9.  Accordingly  1 of  hydrogen  (by 
weight)  is  equivalent  to  9 Al,  12  Mg,  28  Fe,  32  Zn  (really 
31.75).  These  numbers  are  called  the  CHEMICAL  EQUIVA- 
LENTS of  the  metals. 

11.  Careful  experiments,  on  a small  scale  with  accurate 
weighings,  show  that  PER  UNIT  of  weight  of  metal  dissolved 
in  sulphuric  acid,  THE  CRYSTALLIZED  SULPHATES  WEIGH: 
For  Mg,  10.25;  Fe,  4.96;  Zn,  4.38;  Cd,  2.49.  If  carefully 
heated  to  drive  out  the  water  of  crystalization,  the  residual 


SUBSTITUTION  BY  SOLUTION. 


135 


anhydrous  sulphates  weigh  respectively  5.00,  2.71,  2.46  and 
1.85  times  as  much  as  the  metal  used.  Lead  converted  into 
nitrate  weighs  1.60,  into  crystalized  acetate  (sugar  of  lead) 
1.83  per  unit. 

12.  Careful  experiments  of  this  kind  also  permit  the  deter- 
mination of  the  CHEMICAL  EQUIVALENTS  OF  THE  ACIDS 
themselves.  Thus,  since  1 Mg  gives  5.00  dry  sulphate,  the 
equivalent  12  Mg  gives  60  Mg  S^te,  in  which  the  non-metallic 
matter  (the  S^te)  is  60-12=48.  But  the  acid  contains  H=1 
as  metal  or  instead  of  the  metal.  Hence,  the  chemical  equiv- 
alent of  sulphuric  acid,  H is  49.  In  a like  manner,  the 
equivalent  of  nitric  acid  is  found  to  be  63,  and  thaf  of  muri- 
atic acid,  36.5. 


19.  SOLUTION  OF  SILVER  AND  GOLD. 

1.  Dilute  sulphuric  or  muriatic  acids  have  no  effect  what- 
ever on  copper,  mercury  and  silver,  nor  on  gold  and  platinum. 
All  these  metals  are  insoluble  in  dilute  acids.  But  when 
heated  with  CONCENTRATED  sulphuric  ACID,  the  first  three 
dissolve,  yielding  a noxious  gas  having  the  odor  of  burning 
sulphur;  the  last  two,  gold  and  platinum,  remain  insoluble 
even  in  boiling  concentrated  sulphuric  acid. 

2.  Very  dilute  nitric  acid,  in  the  cold,  has  but  little  action 
on  the  first  three  metals  (Cu,  Hg,  Ag),  but  when  the  acid  is 
reasonably  strong — say  10  per  cent. — it  acts  quite  promptly, 
especially  when  moderately  heated.  While  the  metals  dissolve, 
a very  noxious  reddish  gas  (RUTILANT  VAPORS)  is  produced 
in  abundance. 

3.  The  rutilant  vapors  invariably  make  their  appearance 
when  strong  nitric  acid  exerts  its  dissolving  influence.  When 
a filter  paper  or  sponge  with  aqua  ammonia  is  brought  near, 
ABUNDANT  WHITE  CLOUDS  take  the  place  of  the  noxious 
vapors,  which  evidently  combine  with  the  ammonia  to  a white 
solid.  In  this  way,  the  solution  may  be  effected  in  a room 
not  provided  with  hood. 


136 


LECTURE  19. 


4.  Nitric  acid  (AQUA  FORTIS),  even  when  boiled,  has  no 
effect  on  gold  nor  on  platinum;  they  are  insoluble  in  all  ordi- 
nary single  acids.  In  fact,  gold  is  generally  separated  from 
its  alloy  with  silver,  by  boiling  the  alloy  with  concentrated 
sulphuric  acid  or  with  nitric  acid  under  conditions  established 
by  long  practice;  the  amount  of  gold  present  must  be  less 
than  one -fourth  in  the  alloy.  This  accounts  for  the  common 
name  of  nitric  acid  in  german:  Scheide  wasser.  Compare 
this  wet  way  process  with  the  dry  way  separation,  8,  12. 

5.  AQUA  REGIA  (4  muriatic  with  1 nitric  acid)  dissolves 
gold  (foil)  readily.  Both  gold  and  platinum  are  dissolved  by 
moderately  heating  them  with  this  acid  in  large  excess.  When 
all  metal  dissolved,  the  excess  of  acid  is  driven  off,  carefully 
avoiding  overheating,  as  that  would  decompose  the  MURIATE 
obtained  (test,  13,  10).  Dissolving  in  water,  we  have  the 
common  solutions  of  these  two  metals;  muriate  of  gold  and  of 
platinum. 

6.  The  nitrates  of  copper,  mercury  and  silver  are  readily 
obtained  in  crystal  form.  Silver  nitrate  crystallizes  generally 
in  rhombic  tablets,  of  almost  130  degrees.  Silver  and  its  salts 
are  very  sensitive  to  light  and  to  many  gases,  and  even  to 
dust,  so  that  good,  colorless  (or  white)  crystals  can  only  be 
obtained  under  specially  favorable  conditions. 

7.  The  nitrate  of  mercury  obtained  varies  with  the  con- 
ditions under  which  the  metal  is  dissolved.  When  at  com- 
mon temperature,  acted  upon  by  dilute  nitric  acid,  the  resulting 
nitrate  is  precipitated  abundantly  by  the  muriatic  acid  or  by 
salt;  it  is  called  MERCUROUS  NITRATE.  When  the  metal  is 
acted  upon  by  reasonably  strong  acid  on  the  water  bath,  the 
resulting  nitrate  is  not  precipitated  by  muriatic  acid  or  salt; 
it  is  called  MERCURIC  NITRATE. 

8.  The  sulphates  of  mercury  show  the  same  difference. 
Heating  the  metal  with  less  than  half  its  weight  of  concen- 
trated sulphuric  acid  gives  MERCUROUS  sulphate;  while 
heating  mercury  with  twice  its  weight  of  concentrated  acid 
until  the  excess  of  acid  is  driven  off,  gives  MERCURIC  sul- 


SOLUTION  OF  SILVER  AND  GOLD. 


137 


phate.  The  distinction  is  made  as  before  stated;  the  mercu- 
rous solutions  are  precipitated  by  muriates.  The  precipitate 
is  CALOMEL;  the  other  muriate  is  SUBLIMATE. 

9.  When  trying  to  dissolve  the  mercuric  sulphate,  an 
abundant  yellow  precipitate — the  TURPETH  MINERAL — forms, 
a so-called  basic  sulphate,  while  the  balance  or  acid  sulphate 
passes  into  solution.  By  adding  about  5 per  cent  (sulphuric) 
acid  to  the  water,  the  entire  salt  will  be  dissolved,  and  no 
yellow  precipitate  will  form.  When  it  has  formed,  such 
addition  of  acid  will  redissolve  it. 

10.  If  the  residue  from  copper  and  concentrated  acid  is 
taken  up  in  warm  water,  the  resulting  solution  will  deposit 
the  crystals  of  blue  vitriol  described  (15.9). 

In  this  manner  ALL  METALS  HAVE  BEEN  BROUGHT  INTO 
SOLUTION,  excepting  the  modern  light  metals  potassium  and 
sodium  (6.12).  Greenish  iron  solutions  in  presence  of  nitric 
acid  become  reddish;  these  are  called  FERRIC,  the  original 
greenish  FERROUS. 

11.  THESE  SOFT  METALS  have  to  be  kept  in  well  stop- 
pered bottles  under  pure  naphta,  and  even  then  their  surface 
soon  looks  dull  and  corroded.  When  freshly  cut  with  a knife 
the  surface  looks  brilliant  white  like  silver.  Thrown  on  water 
the  metal  floats,  melts  (round  globule)  and  burns  with  a pur- 
ple (Ka)  flame,  finally  exploding;  hence,  the  experiment 
must  be  made  in  a deep  beaker  with  but  an  inch  of  water. 
Sodium  is  less  violent;  burns  with  yellow  flame. 

12.  The  solution  so  obtained  is  strongly  alkaline.  Evapo- 
rated to  dryness  and  fused,  the  CAUSTIC  ALKALIES  are 
obtained.  Made  carefully  in  a large  nickel  crucible,  the  ex- 
periment yields  1.7-1  of  caustic  soda,  1.43  of  caustic  potassa 
per  unit- of  metal. 

It  may  also  be  added  that  a UNIT  WEIGHT  OF  METAL 
GIVES  1.44  Ag  Sate,  1.57  Ag  Nate,  1.60  Pb  Nate,  3.94  blue 
vitriol,  1.48  mercuric  sulphate;  1.24  mercurous  sulphate;  1.18 
calomel  and  1.35  sublimate.  Accordingly,  the  EQUIVALENT 
of  SILVER  is  about  108,  of  lead  104.  See  18,  12. 


20.  REDUCTION  IN  THE  WET  WAY. 


1.  The  four  solvents  used  for  the  solution  of  the 
metals  are  water,  dilute  acids,  concentrated  (single)  acids  and 
aqua  regia.  The  type  metals,  soluble  in  these  solvents,  are 
POTASSIUM,  ZINC,  SILVER  and  GOLD.  To  the  most  soluble 
group  belong  Ka,  Na,  as  shown;  also  Ca,  Sr,  Ba.  Insoluble 
in  water,  soluble  in  dilute  acid  are:  Mg,  Al;  Zn,  Fe,  Pb. 
Requiring  a concentrated  acid  are:  Cu,  Hg,  Ag.  Requiring 
aqua  regia:  Au,  Pt. 

2.  In  each  of  the  four  groups,  the  metals  have  been 
enumerated  according  to  their  DEGREE  OF  SOLUBILITY. 
Thus,  experience  shows  that  Mg  is  clearly  the  most  soluble,  Pb 
the  least  soluble,  of  those  mentioned  in  the  second  group; 
also  Zn  more  soluble  than  Fe,  but  less  soluble  than  Al  and  Mg. 

3.  But  if  into  a blue  copper  solution  a piece  of  iron  be 
thrown,  the  iron  will  become  covered  with  red  copper  and  the 
solution  will  loose  its  fine  blue  color,  soon  appearing  colorless; 
if  exposed  for  hours  to  the  air,  the  iron  now  in  the  solution 
will  show  a rust- like  precipitate.  Evidently,  the  more  soluble 
iron  has  taken  the  place  of  the  less  soluble  copper  in  the  solu- 
tion. We  have  a substitution  of  iron  for  copper. 

4.  This  rule  is  general.  A MORE  SOLUBLE  METAL  WILL 
TAKE  THE  PLACE  OF  ANY  LESS  SOLUBLE  METAL  IN  A 
SOLUTION.  A gold  solution  will  deposit  its  gold  upon  a piece 
of  metallic  silver  and  be  changed  to  a silver  solution.  This 
silver  solution  will  surrender  to  mercury,  a mercury  solution  to 
copper,  the  latter  to  lead,  the  lead  solution  to  zinc. 

5.  THIS  REDUCTION  OF  THE  METALS  IN  THE  WET 
WAY  finds  important  applications  in  the  arts  as  well  as  in  the 
laboratory.  Copper-waters  issuing  in  mining  regions  are 
run  into  large  reservoirs,  and  old  iron  thrown  in;  after  some 
weeks  this  iron  seems  to  have  been  converted  into  copper. 
(Hungary) . 


REDUCTION  IN  THE  WET  WAY. 


131) 


6.  In  the  laboratories,  the  most  elegant  and  conclusive 
TEST  FOR  METALS  IN  THE  WET  WAY  is  this  very  reduc- 
tion by  substitution.  A drop  of  the  solution  to  be  tested  is 
placed  on  a microscope  slide,  and  a minute  clipping  of  a more 
soluble  metal  (generallyzinc)  placed  in  that  drop.  Almost 
instantly  the  substitution  takes  place,  beautiful  crystals  of  the 
metal  in  solution  growing  as  it  were  out  from  the  zinc,  form- 
ing elegant  groupings. 

7.  Even  the  alchemists  were  familiar  with  these  reactions, 
though  some  are  believed  to  have  considered  these  simple 
substitutions  evidences  of  transmutation  of  copper  into  silver, 
of  zinc  into  lead.  A dilute  lead  solution  with  brass  wires  and 
a fragment  of  zinc,  gives  the  old  arbor  saturni  (LEAD  TREE) 
brilliant  crystals  of  pure  lead  coating  the  wires  like  leaves 
and  branches  on  a tree.  A silver  solution  with  mercury  gives 
arbor  dianas,  the  SILVER  TREE,  growing  up  from  the  mer- 
cury. 

8.  By  putting  a weighed  amount  of  the  more  soluble  metal 
into  an  excess  of  a solution  of  the  less  soluble  metal,  an 
EQUIVALENT  amount  of  the  latter  will  be  precipitated  and 
can  be  weighed  after  proper  separation  and  drying.  However, 
for  several  pairs  of  metals  it  is  difficult  to  get  accurate  results, 
the  metals  changing  too  readily. 

9.  It  is  found  that  the  silver  precipitated  weighs  exactly 
nine  times  as  much  as  the  magnesium  used;  hence  the 
chemical  equivalent  of  silver  is  9 times  12  or  108.  For  every 
unit  of  copper  thrown  into  a silver  solution,  3.39  units  of 
the  latter  are  obtained  from  its  nitrate  solution,  especially 
if  the  solution  is  kept  in  a cool  place.  The  equivalent  of  cop- 
per, therefore  is  108,  divided  by  this  number,  or  about  31. G. 
Silver  thrown  into  -a  gold  solution  gives  the  equivalent  of 
gold  about  66. 

10.  THE  CAUSE  of  these  substitutions  is  given  by  the 
facts  of  solubility  of  the  several  metals  taken  singly.  Thus, 
copper  does  not  dissolve  in  dilute  sulphuric,  while  zinc  does 


140 


LECTURE  21. 


so  readily.  If  copper  and  zinc  together  are  thrown  into  the 
same  dilute  acid,  the  zinc  will  dissolve,  the  copper  not.  There 
can  be  no  question  about  these  facts.  Surely,  zinc  is  much 
more  soluble  than  copper. 

11.  Now  if  metallic  zinc  be  thrown  info  a solution  of  blue 
vitriol,  we  have  THE  SAME  THREE  BODIES — zinc,  copper 
and  the  dilute  acid — in  the  same  dish  and  the  same  final 
result  ought  to  be  Obtained,  a zinc  solution  with  metallic  cop- 
per. Such  is  actually  the  case;  zinc  displaces  the  copper 
from  its  solution  because  zinc  is  much  more  soluble  than 
copper. 

12.  The  common  talk  about  CHEMICAL  AFFINITIES  of 
these  metals  is  nothing  but  reasoning  in  a circle,  and  the 
attempt  to  hide  this  false  reasoning  by  the  introduction  of  the 
high  sounding  term.  If  zinc  has  greater  affinity  for  the  acids 
than  the  copper,  nobody  knows  of  that  except  by  the  very 
experiment  which  it  was  attempted  to  explain. 


21.  SULPHUR  AND  SULPHIDES. 

1.  Sulphur  was  known  to  the  ancients.  Already,  Homer 
speaks  of  the  purifying  effects  of  burning  sulphur  (fumiga- 
tion). Its  faint  blue  flame  imparts  pallor  to  the  face  in  the 
dark.  Hence,  the  ancients  burnt  sulphur  at  certain  religious 
ceremonies. 

2.  THE  OLD  CHEMISTS  detected  sulphur  in  many  ores 
which  upon  heating  in  the  open  fire,  emit  the  odor  of  burning 
sulphur  abundantly  (9.  3).  These  ores  generally  having  me- 
tallic luster,  the  ancients  smelting  metals  from  them,  concluded 
that  sulphur  is  a constituent  of  metals  themselves.  Tb  change 
baser  metals  to  gold  seemed  to  the  alchemist  to  involve  simply 
a removal  of  sulphur  or  something  like  sulphur. 

3.  SULPHUR  continues  to  be  a most  important  substance 
to  CHEMICAL  INDUSTRY.  About  400,000  tons,  worth  10 


SULPHUR  AND  SULPHIDES. 


141 


million  dollars,  of  native  sulphur  are  produced  yearly  in  Sicily 
alone,  where  25,000  laborers  dig  for  it. 

For  many  purposes  the  sulphur  of  ores  is  also  available. 
Pyrites  contain  about  50  per  cent,  of  sulphur,  and  occur  in 
immense  deposits  (9.  8). 

4.  Native  sulphur  is  a yellow  solid,  hardness,  and 
gravity  very  near  2.  Its  luster  is  peculiar,  resinous.  It  is  a 
very  poor  conductor  for  heat  and  electricity,  and  very  brittle. 
Fine  specimens  (crystals)  are' transparent.  It  is  readily  fusi- 
ble (113  degrees),  and  on  boiling  (about  450  degrees)  forms 
a brownish  red  vapor,  which  condensed  gives  flowers  of  sul- 
phur as  sublimate.  Melted  sulphur,  cast  in  forms,  gives  roll- 
sulphur.  At  about  200  degrees  melted  sulphur  becomes 
viscid;  above  that  temperature,  it  gets  limpid  again. 

5.  . Sulphur  when  absolutely  pure  has  no  odor,  not  being 
volatile  at  common  temperatures.  When  heated  in  the  open 
vessel,  it  burns  with  a pale  blue  flame  (250  degrees)  far  be- 
low its  boiling  point;  the  gas  produced  is  suffocating,  of  the 
familiar  and  characteristic  odor  of  burning  sulphur. 

Sulphur  is  not  soluble  in  water,  but  quite  soluble  in  essen- 
tial oils,  from  which  it  crystallizes  in  the  forms  exhibited  by 
native  sulphur. 

6.  NATIVE  SULPHUR  CRYSTALS  from  Sicily  (see  p.  69) 
are  very  beautiful  and  often  quite  large.  They  are  (stable  or 
permanent)  rhombic  octahedr^;  OO'  106.6;  sharp  edge  85.0; 
lateral  OO"  143.3.  Quite  generally  the  sharp  corners  are 
truncated  by  the  base  P,  forming  PO  108.4.  The  sharp  edge 
CB  is  also  frequently  truncated  by  the  face  q,  for  which  Pq 
117.8,  Oq  132.5  and  mutually  over  middle  edge,  qq'  124.4. 
Finally  the  edges  PO  are  often  truncated  by  an  obtuse  octa- 
hedron 0,  for  which  Po  134.5.  The  basal  rhomb  has  101.8. 
These  faces  are  readily  identified  even  on  small  crystals  from 
solution. 

7.  MELTED  SULPHUR  CRYSTALLIZES  (p.  69)  upon  cool- 
ing, forming  (unstable)  nearly  square  prisms  MM' 90.6,  cut  off 


142 


LECTURE  21. 


obliquely  by  the  base  P,  so  that  Pa  95.8,  the  face  a replacing 
the  edge  MM'.  The  lateral  corners  are  often  replaced  by  the 
triangular  faces  q,  while  PM  may  be  truncated  by  the  octa- 
hedral 0.  Characteristic  angles  are  MP  94.1;  Ma  135.3. 
Pq  135.1;  qq'  over  P 90.3.  These  dimensions  are  easily 
identified.  Showing  two  different  crystal  forms,  sulphur  is 
said  to  be  DIMORPHOUS. 

8.  SULPHUR  melted  or  as  vapor  COMBINES  WITH  many 
METALS  to  new  bodies,  called  SULPHIDES.  Several  of  these 
artificial  sulphides  are  identic  with  native  sulphides.  Copper — 
in  foil  or  turnings — when  reached  by  the  vapor  of  boiling 
sulphur,  burns  brightly.  The  malleable  copper  used  is  thus 
converted  into  a very  brittle  blueish  black  sulphide. 

9.  Mercury,  silver,  iron,  lead,  zine  and  most  other  ordinary 
metals  combine  in  a like  manner  with  sulphur.  The  coarsely 
divided  metals  (filings,  turnings,  thin  foil,  etc.)  need  only  be 
melted  with  sulphur  in  a crucible. 

Melting  together  equal  weights  of  iron  and  sulphur  gives 
the  BLACK  IRON  SULPHIDE,  very  much  used  in  chemical 
laboratories;  it  is  distinguished  as  FERROUS  SULPHIDE  from 
the  native  yellow  iron  sulphide,  pyrite  (9,  8).  Iron  filings 
mixed  with  flowers  of  sulphur,  and  moistened,  also  give 
ferrous  sulphide — the  mixture  may  even  inflame  (Lemery’s 
Volcano) . 

10.  DUMAS  (portrait  p.  25)  exposed  pure  silver  foil  in  a 
combustion  tube  to  the  vapors  of  sulphur,  and  obtained  finely 
crystallized  silver  sulphide.  He  found  1.148  of  sulphide  per 
unit  of  silver  used.  The  increase  of  14.8  per  cent,  of  silver 
(equivalent  108)  gives  16  as  the  chemical  EQUIVALENT  OF 
SULPHUR. 

11.  If  fragments  of  charcoal  are  heated  in  a combustion 
tube  while  vapors  of  sulphur  are  passed  over  them,  a very 
volatile,  highly  inflammable  liquid  is  formed,  which  will  con- 
dense in  a cooled  receiver.  It  is  called  CARBON  BISULPHIDE, 
and  is  the  best  solvent  for  sulphur,  taking  up  nearly  half  its 


SULPHUR  AND  SULPHIDES. 


143 


weight  at  common  temperatures.  From  this  solution,  splendid 
sulphur  crystals  can  be  obtained. 

12.  GUN  POWDER  IS  A MIXTURE  of  sulphur,  carbon  and 
nitre  in  the  proportion  1:  1:  6.  Washing  with  water  removes 
the  nitre,  the  identity  of  which  will  be  revealed  by  its  prismatic 
crystal  form,  (15,  10).  The  well  dried  residue  yields  sulphur 
to  the  bisulphide,  from  which  fine  crystals  readily  deposit, 
showing  the  octahedron  O,  the  base  P,  and  frequently  the 
truncature  q,  all  readily  identified  by  the  figures  given,  using 
a magnifier.  Insoluble,  black  carbon  finally  remains.  Thus 
the  gun  powder  was  ANALYZED,  separated  into  its  constitu- 
ent parts. 

22.  HYDROGEN  SULPHIDE  AND  METALS. 

1.  Ferrous  sulphide  (21.9)  covered  with  almost  any  diluted 
acid,  gives  strong  effervescence,  both  in  bulk  of  gas  produced 
and  in  odor.  The  latter  is  that  of  rotten  eggs.  This  reaction  or 
chemical  process  is  readily  understood.  The  acid,  say  H 
Muriate  with  Ferrous  Sulphide  gives  HYDROGEN  SULPHIDE 
GAS  and  Ferrous  Muriate  remains  in  the  green  solution. 
Rouelle  first  noticed  this  gas,  which  Scheele  soon  after  studied 
thoroughly. 

2.  In  this  reaction,  the  substances  taken,  H Mr^te  and  Fe^us 
Side,  yielding  Fe^^s  Mr^te  and  FI  S^^®  gas,  have  evidently 
interchanged  their  constituents.  They  are  said  to  have  under- 
gone DOUBLE  DECOMPOSITION— in  this  case  by  VOLATIL- 
IZATION, the  product  being  a gas.  Such  reactions  are  very 
common  in  chemistry. 

3.  HYDROGEN  SULPHIDE  GAS  is  quite  soluble  in  water, 
to  which  it  imparts  a strong  and  highly  characteristic  odor. 
When  left  exposed  to  the  air,  such  sulphuretted  water  soon 
becomes  opalescent,  and  gradually  a white  deposit  forms — this 
is  finely  divided  sulphur  (white  streak,  substance  yellow). 
Some  springs  produce  such  sulphuretted  water  in  abundance, 
and  are  very  valuable  medicinally. 


144 


LECTURE  22. 


4.  Silver  coin  and  ware,  especially  when  moist,  turns 
black  when  exposed  to  the  gas  or  the  water;  lead  paint  and 
compounds  of  lead,  bismuth,  silver  and  other  metals,  also  turn 
promptly  brown  or  black.  Accordingly,  hydrogen  sulphide  is 
a most  IMPORTANT  REAGENT  by  means  of  which  heavy 
metals  can  be  recognized.  During  working  hours,  the  chemi- 
ical  laboratories  keep  this  gas  on  tap  in  a large  Kipp  genera- 
tor for  constant  use. 

5.  A lead  solution  of  ordinary  working  strength — say  one 
per  cent — is  perfectly  colorless  and  transparent.  A few  bubbles 
of  the  hydrogen  sulphide  gas  passed  into  it  almost  instantly 
blackens  it,  forming  an  abundant  black  precipitate  of  Pb  Side, 
settling  soon  to  the  bottom.  Even  when  extremely  dilute,  a 
brownish  coloration  will  be  produced  in  lead  solution  by  H 
Side  gas.  This  gas  is  the  most  sensitive  reagent  known  for 
lead  in  solution.  For  this  reason,  lead  solutions  are  replaced 
by  barium  solution  as  reagent  for  sulphates  (13,  12). 

6.  The  black  lead  sulphide  PRECIPITATE  being  solid,  may 
be  readily  separated  from  the  liquid  by  FILTRATION,  and  by 
WASHING,  best  adding  a little  hydrogen  sulphide  to  the 
wash  water;  drying  then  removes  both  water  and  excess  of 
hydrogen  sulphide. 

This  precipitate  is  not  only  insoluble  in  water  but  also  insol- 
uble in  dilute  acids  (nitric,  acetic  must  be  tried  for  sulphuric 
and  muriatic  produce  precipitates  themselves,  13.8). 

7.  This  reaction  evidently  again  is  a double  decomposition, 
for  both  substances  taken  interchange  constituents.  The  lead 
acetate  and  hydrogen  sulphide  gas  give  lead  sulphide  and 
hydrogen  acetate  (acetic  acid).  But  it  differs  from  the  pre- 
ceding case  (2)  by  the  product  being  an  insoluble  instead  of 
a volatile  compound.  The  present  reaction  is  therefore  a 
DOUBLE  DECOMPOSITION  BY  PRECIPITATION. 

8.  It  is  evident  that  all  SULPHIDES  INSOLUBLE  IN 
DILUTE  ACID  will  precipitate  by  sulphide  gas  in  acidified 
solutions.  The  corresponding  metals  which  thus  may  be 


HYDROGEN  SULPHIDE  AND  METALS. 


145 


precipitated  as  sulphides  are,  in  proper  groupings:  a)  Ag 
Hgous,  pb;  b,  Cu,  Hgic.  Cd,  Bi;  c)  As,  Sb,  Sn;  d)  Au,  Pt. 
They  are  distinguished  a)  by  precipitate  with  muriates  (their 
muriates  insoluble)  ; c and  d,  the  sulphide  precipitates  soluble 
in  yellow  Am  Solution  of  c colorless,  d yellowish. 

9.  YELLOW  AMMONIUM  SULPHIDE  is  obtained  by  satur- 
ating aqua  ammonia  with  hydrogen  sulphide  gas,  and  perhaps 
dissolving  some  flowers  of  sulphur  in  it.  The  precipitate  is 
tested  while  still  on  the  filter,  but  completely  washed  with 
water,  so  that  the  washing  is  entirely  free  from  acid  reaction  (a 
drop  making  no  red  stain  on  blue  test  paper).  If  the  acid  were 
not  completely  removed,  it  would  decompose  the  reagent, 
giving  hydrogen  sulphide  gas  and  an  abundant  precipitate  of 
sulphur. 

10.  The  other  heavy  metals  (not  precipitated  by  hydrogen 
sulphide  gas  because  their  sulphides  are  soluble  in  dilute  acids) 
do  come  down  when  the  solution  is  made  ALKALINE  by  a rea- 
sonable excess  of  ammonium  hydrate  (suificient  to  give 
the  odor).  These  metals  are  f)  Zn,  Mn,  Fe^us,  Co 
and  g)  Al,  Fe’c>  Chc-  In  case  of  Ferric,  the  hydrogen  sul- 
phide first  makes  the  solution  opalescent  (from  separation  of 
S)  and  ferrous,  then  precipitates  this  black. 

H.  The  two  groups  f and  g are  readily  distinguished  by 
the  latter  giving  a precipitate  by  ammonium  hydrate  after  the 
solution  has  been  treated  with  an  excess  (as  solvent)  of  am- 
monium muriate,  while  the  metals  grouped  under  f do  not  give 
a precipitate  under  these  conditions  i.  e.  their  HYDRATE  is 
SOLUBLE  IN  SAL  AMMONIAC  (or  ammonium  muriate). 

12.  THE  LIGHT  METALS,  Ka,  Na  and  Mg,  Ca  are  not  pre- 
cipitated by  hydrogen  sulphide  gas  under  any  conditions,  their 
sulphides  being  soluble  in  water.  Thus,  the  metals  in  solu- 
tion are  almost  as  readily  distinguished  by  means  of  hydrogen 
sulphide  gas  and  a few  other  reagents  as  by  the  blowpipe 
in  the  dry  way.  We  shall  soon  return  to  this  most  important 
subject  of  CHEMICAL  ANALYSIS  IN  THE  WET  WAY. 


146 


LECTURE  22. 


Note. — The  following  preliminary  tabular  exposition  of  the  course 
IN  WET  WAY  ANALYSIS  FOR  METALS  Comprises  only  the  general  reactions 
determining  the  groups,  and  the  special  features  which  in  these  reactions 
mark  the  individual  members.  These  are  the  only  reactions  sufficiently 
explained  in  the  preceding.  Only  one  metal  is  here  supposed  to  be  in 
the  solution,  which  thus  contains  a simple  compound  only  and  is  not 
complex. 

1.  Solution -f- 11  Mrate — white  precipitate — Silver  Group  I.  Pre- 

cipitate soluble  in'much  water,  Pb  ; precipitate  soluble  in  Am  Hate. 
Ag;  insol.,  turning  black,  Hgous. 

2.  Solution-j-  11  Sate,  white^precipitate.  Barium  Group,  IF.  Very  dilute 

solution,  no  precipitate,  Ca;  a precipitate  forms  promptly,  Ba, 
very  slowly,  Sr.  If  solution  black  by  H Side,  it  contains  Pb, 
from  r. 

3.  Acidified  (mur)  solution,  saturated  with  H Side  gas  gives  a precipitate 

(other  than  merely  S)  . . IH,  IV,  V.  The  precipitate  washed 

and  treated  with  yellow  Am  Side  remains  insoluble,  III;  or  dis- 
solves IV,  V. 

III.  Copper  Group.  Original  solution  blue  or  green  . , Cu. 

Precipitate  first  whitish,  then  yellowish,  brownish,  finally 
black  . . Hgic;  precipitate  yellow  . . Cd;  brown  . . Bi. 

Precipitate  soluble  in  yellow  Am  Side;  original  solution  color- 
less, . . IV ; yellow  to’brownish  . . V. 

IV.  Arsenic  Group. — Color  of  sulphide  precipitate  yellow, . As ; 
orange  . . Sb;  brownish  . . Sn. 

V.  Gold  Group. — Original  solution  precipitated  brownish  by 
ferrous  solution  . . Au;  yellow  by  sal  ammoniac  solution  . . Pt. 

4.  Solution  (3)  made  alkaline  with  ammonia  after  adding  considerable 

Am  MrMe;  a precipitate  forms  VI  or  VII. 

Original  solution  with  excess  sal  ammoniac,  made  strongly  alka- 
line with  Am  Hate,  np  precipitate,  VI;  a precipitate  VII. 

VI.  Zinc  Group.  Original  solution,  deep  green,  Ni;  pink,  Co; 
pale  rose,  Mn ; pale  green,  turning  rusty,  Feo^s;  colorless,  Zn. 

Am  Side  precipitate=white,  Zn ; flesh  colored,  Mn  ; black,  Feo^s, 
Ni,  Co,  distinguished  by  color  of  original  solution  (or  dry  way 
borax  bead,  6,  1 1). 

VII.  Aluminium  Group.  Original  solution,  colorless,  A1 ; 
green,  Cr;  yellow  to  orange,  Feic.  The  precipitates  have  nearly 
the  same  colors. 

5.  If  no  precipitate  obtained  : Magnesium  group,  VIII.  Solution  with 

much  sal  ammoniac,  made  strongly  alkaline  with  Am  Hate;  to  por- 
tions of  this  mixture,  add 

a)  Am  Cate;  a precipitate  forms,  or  at  least  on  adding  Am 
Oxalate  . . Ca  from  H. 

b)  Na  pate,  white  crystalline  precipitate  . . Mg. 


HYDROGEN  SULPHIDE  AND  METALS. 


147 


Original  solution  or  substance,  with  Ka  IDte,  odor  of  ammonia; 
red  paper  turned  blue  . . Am. 

Flame  coloration,  persistent  and  intense  yellow  . . . Na, 

purplish,  and  through  blue  glass  deep  reddish  . . . Ka. 

It  is  understood  that  the  tests  are  carried  on  till  the  substance  is  found, 
not  beyond  (for  simple  solutions),  throughout  this  course.  Thus,  if 
found  in  reaction  i,  none  of  the  others  is  tried;  if  in  5,  reaction  gives  a 
precipitate,  that  ends  it.  For  diagram  of  this  course  see  p.  73. 


23.  IODINE  AND  IODIDES. 

1.  Iodine  is  a solid  substance  which  in  many  respects  re- 
sembles sulphur,  especially  in  its  action  on  metals.  While 
now  in  the  market  of  chemicals  because  of  its  many  applica- 
tions, it  was  not  known  till  1811,  when  COURTOIS  discovered 
it  in  ashes  from  sea  weeds.  It  is  mainly  obtained  from  the 
mother  liquors  of  Chili  saltpeter. 

2.  IODINE  is  a grayish  black  solid,  sufficiently  volatile  to 
make  its  offensive  and  characteristic  odor  perceptible  at 
common  temperatures.  Its  main  properties  are:  G 4.50,  F 
113  and  B 180  degrees.  Its  vapors  have  a beautiful  deep 
violet  (Greek:  iodos)  color;  hence  its  name  and  chemical 
symbol  lo.  It  is  sufficiently  soluble  in  water  to  tinge  it  yellow. 
It  is  more  soluble  in  alcohol,  and  abundantly  soluble  in  chloro- 
form and  carbon  bisulphide. 

3.  Both  from  solution  and  by  sublimation  it  crystallizes 
quite  readily.  On  account  of  its  marked  volatility,  IODINE 
CRYSTALS  are  not  permanent,  but  disappear  and  form  again 
in  the  containing  vessels,  according  to  the  changes  in  tempera- 
ture. The  crystals  are  rhombic  tablets.  Compared  to  the 
sulphur  crystals  (p.  69)  the  angles  are  OO"  136  and  PO 
112  degrees. 

4.  Starch  paste  is  colored  deep  blue  by  iodine;  the 
color  disappears  on  heating  to  about  the  boiling  of  water,  but 
promptly  re-appears  on  cooling.  This  reaction  is  one  of  the 
most  delicate  or  sensitive  we  have  in  the  wet  way.  The 
merest  trace  of  iodine  in  solution  can  be  revealed  by  this 
TEST.  One  part  of  iodine  in  a million  of  solution  will  show 


148 


LECTURE  23. 


the  color  with  starch  paste;  in  10  cc  of  such  a solution  there 
is  the  hundredth  part  of  a milligram  of  iodine. 

5.  Passing  hydrogen  sulphide  gas  through  a solution  of 
iodine  in  chloroform  or  bisulphide  under  water,  the  intense  red 
color  will  gradually  disappear  and  the  water  will  become  turbid 
from  sulphur.  This  is  evidently  a substitution  of  iodine  for 
sulphur.  lo  and  H Side  giving  S and  H loide.  Decant,  filter 
and  by  gentle  heating  drive  off  the  excess  of  H Side,  and  a 
strong  solution  H loide  or  HYDRIODIC  ACID  remains.  This 
colorless  solution  gradually  decomposes,  setting  free  iodine,  as 
indicated  by  the  yellow  color  it  assumes. 

6.  Finely  pulverized  metallic  arsenic  thrown  into  a solution 
of  iodine  in  bisulphide,  combines  with  the  iodine,  forming 
ARSENIC  IODIDE,  which  separates  in  brick  red,  brilliant, 
thin  tablets  upon  the  volatilization  of  the  solvent.  This  As 
lo^de  is  readily  fusible  and  volatile;  it  sublimates  without 
decomposition  (Synthesis). 

7.  Iodine,  like  sulphur,  unites  with  most  metals  in  the 
dry  way.  Heating  a glass  vessel  containing  a little  mercury, 
this  will  deposit,  by  distillation,  in  small  metallic  globules  on 
the  inner  walls  of  the  vessel.  When  this  has  cooled  again, 
heat  an  equal  weight  of  iodine  in  the  same;  as  the  violet 
vapors  reach  the  mercury,  they  combine  therewith,  forming 
crystals  of  MERCURIC  IODIDE. 

8.  Mercuric  iodide  can  be  readily  moved  from  one  place  to 
another  by  heat;  it  will  deposit  by  sublimation  on  the  colder 
parts  of  the  vessel.  At  first  it  forms  YELLOW  prismatic 
crystals  of  114.5  degress.  Gradually  it  turns  BRILLIANT 
RED;  this  change  may  be  produced  instantly  by  rubbing  the 
yellow  crystals  with  any  hard  body  (a  glass  rod).  The  red 
crystals  are  generally  tabular,  with  a pyramid  inclined  under 
1(H). 5 degrees  to  the  base ; hence  quadratic  (10.3).  Mercuric 
iodide  is  DIMORPHOUS  (21,  V). 

9.  THE  SMALLEST  TRACE  OF  MERCURY  may  be  posi- 
tively IDENTIFIED  in  the  dry  way  by  applying  these  reactions 


IODINE  AND  IODIDES. 


149 


in  a small  blowpipe  test  tube  of  hard  glass,  and  observing 
the  results  with  a magnifier  and  under  the  microscope.  The 
metal  is  identified  by  the  distillate  consisting  of  minute  white 
globules,  having  brilliant  metallic  luster.  The  iodide  is  next 
formed  by  synthesis,  its  colors  and  crystal  forms  recognized. 
This  series  of  tests  is  important  in  toxicology. 

10.  Iron,  in  the  presence  of  water,  combines  readil}^  with 
iodine,  forming  FERROUS  IODIDE,  which  being  freely  soluble 
in  water,  is  purified  by  simple  filtration.  See  21.9. 

With  potassium  carbonate,  Ka  C^te,  there  will  form  a pre- 
cipitate containing  the  iron  (as  shown  by  blowpipe)  and  from 
the  filtrate,  permanent  CUBICAL  CRYSTALS  of  potassium 
iodide  are  obtained.  Fe^us  loide  and  Ka  give  Fe^us  c^te 
(insol)  and  Ka  lo^^^  (sol).  By  synthesis,  the  iron  takes  the 
iodine,  and  by  double  decomposition  this  is  transferred  to  the 
potassium. 

11.  Potassium  iodide  is  the  most  important  soluble  iodide; 
by  its  means  the  INSOLUBLE  IODIDES  are  readily  obtained 
as  PRECIPITATES  from  the  solution  of  the  metals.  Thus  Pb 
loide,  yellow;  hexagonal  tablets  readily  crystallize  from  solu- 
tion in  hot' water.  FIgic  red;  first  pink,  then  rose,  finally 
brilliant  red;  soluble  in  excess  of  reagent,  Ka  lo'^^  to  colorless 
solution.  Mercurous  solutions  give  dirty  green  Hgous  loUe  as 
precipitate.  Ag  lo'^^  is  yellowis<h  white,  insoluble  in  ammonia 
(distinction  from  muriate).  Bi  loi^®  is  brown.  All  other 
iodides  are  soluble,  hence  not  obtainable  by  precipitation. 

12.  NlTRO-NlTRIC  ACID  (concentrated  nitric  acid  sat- 
urated with  rutilant  vapors,  19.2)  instantly  SETS  FREE  TFIE 
IODINE  OF  IODIDES;  the  free  iodine  may  be  recognized  by 
its  color,  solubility  in  chloroform  and  the  starch  reaction,  4. 
Shaking  the  solution  with  chloroform,  the  free  iodine  will  col- 
lect in  this  solvent,  tinging  it  deep  red,  while  the  aqueous 
solution  becomes  colorless.  Now  making  the  solution  alkaline, 
the  iodide  is  reproduced,  and  the  chloroform  loses  its  color. 
Such  operations  with  NON-MISCIBLE  SOLVENTS  (as  water 
and  chloroform)  are  very  important,  especially  in  toxicology. 


24.  ACIDIMETRY  AND  ALKALIMETRY. 


1.  Vinegar  and  lime  are  the  oldest  representatives  of  two 
important  classes  of  substances  endowed  with  opposite  charac- 
ters; namely  ACIDS  AND  BASES  (13).  Muriatic,  nitric  and 
sulphuric  acids  correspond  to  the  first;  the  caustic  alkalies  to 
the  second.  Stronger  solutions  of  these  substances  are  cor- 
rosive; when  exceedingly  diluted,  the  former  taste  sour  (acid), 
the  latter  not.  Add  the  strong  acid  to  the  water  while  stirr- 
ing, when  diluting. 

2.  But  certain  coloring  materials  are  most  sensitive  INDI- 
CATORS of  the  presence  of  either  of  these  bodies,  so  that  the 
dangerous  method  of  tasting  never  is  resorted  to  by  chemists. 
The  most  common  indicators  are  litmus,  cochineal  and  phenol- 
phthalein.  A drop  of  these  solutions  show  even  with  exceeding 
dilute  solutions  of  acid  or  base:  litmus,  red  and  blue;  cochin- 
eal, orange  and  purplish  red;  phthalein,  colorless  and  deep  red. 

3.  Pure  water,  alcohol  and  kindred  liquids  do  not  change 
the  color  of  these  indicators.  Such  liquids  are  said  to  be  neu- 
tral, or  to  have  a neutral  reaction.  The  extreme  sensitive- 
ness of  the  indicators  or  the  extraordinary  DELICACY  OF 
THE  REACTION  may  be  shown  by  adding  a single  drop  of 
dilute  alkali  solution  to  half  a beaker  full  of  water  tinted 
ruby  red  by  a drop  of  cochineal  tincture;  on  stirring  it  turns 
instantly  purplish  red.  A drop  of  an  equivalent  acid  solution 
turns  it  ruby  red,  the  next  turns  it  orange. 

4.  THESE  CHANGES  CAN  BE  REPEATED  an  indefinite 
number  of  times,  most  conveniently  by  having  acid  and  base 
in  two  BURETTES.  The  liquid  must  be  well  mixed  after  the 
addition  of  each  drop,  best  by  giving  a circular  motion  to  the 
beaker  glass.  The  change  will  be  sudden  upon  the  addition 
of  a single  drop;  really  half  of  this  drop  saturates  the  remain- 
ing acid,  the  other  half  causes  the  final  change  in  color  or 
reaction. 


ACIDIMETRY  AND  ALKALIMETRY. 


151 


5.  In  this  manner  THE  RELATIVE  STRENGTH  or  chemical 
equivalents  of  given  solutions  of  acid  and  bases  are  readily 
DETERMINED.  Suppose  that  5 cc  of  an  acid  solution,  with 
water  and  phthalein,  shows  no  change  upon  the  addition  of 
7.8  cc  of  alkali,  but  at  7.85  suddenly  turns  red;  then  7.85  cc 
of  this  alkali  are  equivalent  to  5 cc  of  the  acid.  This  alkali 
solution  is  accordingly  1.57  times  as  strong  as  that  acid. 

6.  If  now  the  strength  of  the  acid  be  known,  that  of  the 
alkali  will  have  become  determined  by  the  operation.  In 
VOLUMETRIC  CHEMICAL  ANALYSIS  the  unit  of  the  strength 
of  solutions  is  NORMAL  (N),  and  CONTAINS  ONE  MILLI- 
GRAMME-EQUIVALENT PER  CUBIC  CENTIMETER.  If  the 
acid  used  above  was  normal,  then  the  alkali  found  is  1.5  N. 
The  equivalent  of  sodium  hydrate  being  40  (as  we  soon 
shall  learn),  it  would  contain  1.57  times  40  or  62.8  mgr.  per 
cc  in  the  above  instance.  This  is  ALKALIMETRY. 

7.  The  unit  of  the  chemical  equivalent  being  hydrogen 
(18,  9,  10)  the  strength  of  the  acid  is  established  by  MEASUR- 
ING THE  HYDROGEN  GAS  evolved  from  a measured  volume 
of  the  acid  acting  upon  an  excess  of  magnesium  ribbon.  Thus, 
suppose  that  5 cc  of  the  dilute  acid  had  been  taken,  and  75  cc 
hydrogen  gas  had  been  obtained,  while  a considerable  amount 
of  magnesium  remained  undissolved;  then  1 cc  acid  gave 
15  cc  gas  or  the  acid  is  1.25  N.  This  is  ACIDIMETRY. 

8.  If  a number  of  careful  determinations  concordantly  give 
that  result  (1.25  N),  a stock  of  NORMAL  ACID  will  be  ob- 
tained by  diluting  100  cc  to  125  or  adding  to  a liter  of  the  acid 
a quarter  liter  of  water.  Since  the  equivalent  of  sulphuric 
acid  is  49  (18.12),  the  normal  acid,  if  sulphuric,  contains  49 
mgr  of  acid  per  cubic  centimeter;  if  nitric,  63  mgr;  if  muriatic. 
36.5  mgr. 

9.  Having  thus  obtained  a stock  of  normal  acid,  it  is  easy 
to  prepare  a corresponding  stock  of  NORMAL  ALKALI  (see 
6).  With  these  normal  solutions  the  unknown  strength  of 
acids  and  bases  is  determined  in  the  manner  indicated.  As  a 


152 


LECTURE  24. 


matter  of  fact,  the  specific  gravity  of  normal  hydrates  (Ka  or 
Na)  is  about  1.044,  of  sulphuric  and  nitric  acids' about  1.032 
and  muriatic  about  1.016.  Hence,  if  solutions  run  from  1.05 
to  1.10  they  are  suitable  for  making  normal  solutions. 

10.  Not  one  of  these  alkalies  or  acids  is  obtainable  in  the 
free  state  in  exactly  weighable  condition;  hence,  the  pre- 
ceding method  of  standardizing  by  means  of  an  accurately 
weighed  metal  is  necessary.  It  has,  however,  been  found, 
that  pure  and  CRYSTALLIZED  OXALIC  ACID  is  permanent 
in  air,  when  kept  in  well  stoppered  bottles.  Numerous  and 
careful  experiments  have  shown  its  equivalent  to  be  63.  By 
evaporating  a normal  solution  of  pure  caustic  alkali  in  a silver 
dish  and  fusing  the  residue,  the  equivalent  of  caustic  soda  is 
found  to  be  40,  that  of  caustic  potassa  56,  approximately. 

11.  Hence,  63  mgr  of  crystallized  oxalic  acid,  represents  1 
cc  normal  acid.  TO  TEST  ANY  ALKALI  SOLUTION,  it  is  only 
necessary  to  weigh  off  as  accurately  as  possible,  say  630  mgr 
of  such  crystallized  oxalic  acid,  transfer  to  beaker,  add  water 
and  indicator  (best  phthalein)  ; this  represents  10  cc  N.  If 
now  the  alkali  is  run  in— first  rapidly,  then  drop  by  drop— and 
suddenly  turns  the  liquid  permanently  red  when  9.85  have 
been  used,  it  is  not  exactly  normal,  but  985  cc  filled  up  to  a 
liter,  will  be  normal. 

12.  The  books  generally  recommend  the  proportion  of  nor- 
mal solution  of  oxalic  acid;  this  is  inadvisable  for  many  rea- 
sons. The  above  manner  of  using  the  pure  acid  BY  WEIGHT 
IS  by  far  the  best  and  MOST  ACCURATE.  If  a solution  is 
wanted,  only  half  normal  should  be  made,  since  a normal 
oxalic  acid  solution  is  almost  saturated. 

Starting  with  oxalic  acid,  the  normal  alkali  will  be  obtained 
first,  and  by  its  means  the  normal  acid  for  use. 


25.  NEUTRALIZATION  AND  CALORATION. 


1.  THE  NORMAL  SOLUTIONS,  prepared  according  to  the 
methods  indicated,  are  very  useful.  They  permit  the  ready 
determination  of  the  strength  of  given  substances,  as  shown. 
They  also  enable  us  to  establish  chemical  laws  and  determine 
important  chemical  equivalents. 

2.  Mixing  equal  volumes — measured  by  burette  or  pipette — 
of  normal  solution  of  base  and  acid,  we  obtain  a NEUTRAL 
substance  in  solution;  the  process  is  called  NEUTRALIZATION. 
If  we  take  10  cc  N nitric  acid  and  add  10  cc  N potassium 
hydrate — careful  evaporation  will  soon  show  the  formation  of 
the  familiar  prismatic  CRYSTALS  of  potassium  nitrate  (15.10). 
In  the  same  manner,  sodium  hydrate  and  muriatic  acid  yield 
the  cubical  crystals  characteristic  of  sodium  muriate  or  salt 
(11.8). 

3.  If  the  mixed  solution  is  carefully  distilled,  a salt  residue 
remains  in  the  flask,  and  the  distillate  is  pure  water.  Accord- 
ingly, Ka  Hate  and  H Nate  giving  Ka  Nate  and  H Hate  by  double 
decomposition,  (22,  2,  7) , this  HYDROGEN  HYDRATE  FORMED 
IS  WATER.  That  is,  equivalent  amounts  of  acid  and  base 
neutralize  each  other,  forming  a-  salt  and  water.  Thus  we 
have  a third  kind  of  double  decomposition,  namely  by  neu- 
tralization. 

4.  If  say  10  cc  of  normal  solution  are  taken,  the  amount  of 
the  compound  is  exactly  10  milligramme-equivalents  (24,  6). 
The  mixture  carefully  evaporated  to  dryness  or  to  crystalliza- 
tion, and  completing  the  crystallization  by  spontaneous 
evaporation — the  weight  of  the  salt  formed  represents  also  10 
mgr.  equivalents,  and  will  allow  the  DETERMINATION  OF 
THE  EQUIVALENT  OF  THE  BASE  if  that  of  the  acid  is  known. 
The  salt  is  the  acid  in  which  hydrogen  has  been  replaced  by 
the  metal  ( 18,  6) . 


154 


LECTURE  25. 


5.  Thus  10  cc  normal  solution  of  pure  Ka  H^te  and  as  10  cc 
normal  solution  of  H yield  10  milligramme-equivalents  of 
crystals  of  potassium  nitrate;  the  residue  weighing  1010  mgr, 
the  equivalent  of  Ka  is  101.  But  that  of  H is  63, 
(18,  12) ; the  difference  101 — 63=38  represents  the  excess  of 
the  equivalent  of  potassium  over  that  of  hydrogen  displaced. 
Hence  the  EQUIVALENT  OF  POTASSIUM  is  39.  The  corres- 
ponding residue  of  the  sulphate  is  870  mgr,  that  of  the  muriate 
745  mgr;  they  give  the  same  value  for  Ka. 

6.  Corresponding  determinations  with  normal  sodium 
hydrate  solutions  give  the  CHEMICAL  EQUIVALENT  OF  SO- 
DIUM 23.  In  the  same  manner,  the  equivalent  of  AMMONIA 
is  found  to  be  18. 

For  sodium,  direct  determinations  of  the  equivalent  are  pos- 
sible, though  not  as  accurate,  because  the  fresh  cut  sodium 
corrodes  quite  promptly,  and  the  action  of  the  water  is  rather 
too  violent.  See  18,  8,  taking  water  instead  of  dilute  acid.' 

7.  Instead  of  measured  amounts  of  normal  hydrates,  care- 
fully weighed  amounts  of  CARBONATES  (16,  3)  may  be  used 
exactly  as  the  metal  in  18,  8.  If  the  carbonate  is  in  form  of 
crystal  or  cleavage  piece  (calcite),  the  solid  may  be  placed  on 
the  slanting  dry  wall  of  the  tube,  as  was  the  metal.  If  a 
powder,  it  may  be  weighed  in  a small  porcelain  boat,  and  this 
■placed  in  the  tube. 

8.  In  this  way,  12  cc  gas  (fixed  air)  are  obtained  from  the 
following  number  of  milligrams  of  NATIVE  CARBONATES: 
magnesite  42,  dolomite  46,  calcite  50,  siderite  58,  smithsonite 
63,  strontianite  74,  witherite  98,  malachite  110,  cerussite 
133.5.  Also  from  the  following  amounts  of  ARTIFICIAL  CAR- 
BONATES: Na  53,  Ka  70,  Cd  86,  Hg'c  130  and  bicarbonates: 
Na  42,  Ka  50.  All  these  weights  are  RELATIVELY  EQUIVA- 
LENT, producing  the  same  amount  of  fixed  air. 

9.  It  is  easy  to  show  that  these  numbers  are  true  equiva- 
lents, or  that  EQUAL  VOLUMES  OF  FIXED  AIR  AND  HYDRO- 
GEN ARE  EQUIVALENT.  For  if  equivalent,  the  values  for 


NEUTRALIZATION  AND  CALORATION. 


155 


Na  and  Ka  carbonates  give  upon  subtracting  the  equivalent  of 
the  metal  (23  and  39)  the  same  number  30  as  the  equivalent 
for  Xhis  subtracted  from  smithsonite,  siderite,  cerussite 

leaves  for  the  metals  Zn,  Fe,  Pb,  the  numbers  33,  28,  103.5, 
precisely  as  found  before  (18,  10  and  19,  12). 

10.  Accordingly,  THE  EQUIVALENT  of  C^te  is  30,  and  fixed 
air  is  equivalent  with  hydrogen,  measure  for  measure.  For 
dolomite  46,  the  metal  equivalent  is  16  which  is  half  of  that  of 
the  constituent  metals  Mg  12  and  Ca  20.  In  the  same  way 
sodium  bicarbonate  gives  12  and  potassium  bicarbonate  20, 
exactly  half  the  sum  of  the  metal  and  hydrogen.  From  cal- 
cium we  find  20,  from  calcite  50. 

11.  When  equal  volumes  of  normal  acid  and  base  are 
mixed,  THE  TEMPERATURE  RISES  ABOUT  7 DEGREES;  a 
trifle  more  with  sulphates,  a little  less  with  muriates.  The 
unit  of  heat  is  the  gramme-degree  (gr°),  the  amount  of  heat 
required  to  raise  the  temperature  of  one  gramme  (cc)  of  water 
one  degree  (centigrade).  Using  100  cc  of  each,  1400  gr°  heat 
are  produced  by  100  milligramme-equivalents  of  acid  and 
base.  ' 

12.  One  milligramme-equivalent  of  base  uniting  with  one 
milligramme-equivalent  of  acid  therefore  produces  a CALORA- 
TION OF  ABOUT  14  GRAMME-DEGREES  OF  HEAT  in  forming 
a salt.  Here  only  the  soluble  bases  (alkalies)  have  been  con- 
sidered. Numerous  accurate  determinations  of  caloration  have 
been  made  by  THOMSEN  of  Copenhagen  and  BERTHELOT 
of  Paris. 


26.  FLUX  AND  GLASS. 

1.  MANY  SUBSTANCES  ARE  INSOLUBLE  IN  WATER  AND 
IN  ACIDS,  even  upon  boiling.  Quite  a number  of  silicates 
and  some  precipitates  are  of  this  kind.  Such  are  most  of  the 
gems  (10)  and  the  minerals  Nos.  7 to  12  in  11,  5.  Barium 
sulphate  and  silver  muriate  are  the  most  common  precipitates 


156 


LECTURE  26. 


insoluble  in  acids.  To  examine  such  materials  in  the  wet 
way,  they  must  be  brought  into  solution. 

2.  To  effect  this,  the  insoluble  material  is  most  finely 
pulverized  and  mixed  with  a large  excess  of  alkaline  carbon- 
ates. The  mixture  is  fused  (FLUXED)  in  a platinum  vessel, 
and  maintained  in  the  liquid  state  for  some  time.  Ordinarily 
a DOUBLE  DECOMPOSITION  BY  FUSION  takes  place,  so  that 
the  cooled  mass  is  partly  soluble  in  water,  and  the  residue 
left  by  water  is  soluble  in  acids. 

3.  For  example,  the  absolutely  insoluble  Ba  S^te  precipi- 
tate, mixed  with  a large  excess  of  Ka  C^te  gives,  upon  pro- 
longed fusing,  a mass  from  which  water  readily  extracts  the 
excess  of  Ka  taken  and  the  Ka  S^te  formed  by  double  de- 
composition. The  residue  of  Ba  C^te  is  insoluble  in  water, 
but  readily  soluble,  with  effervescence,  in  nitric  acid,  giving 
Ba  in  aqueous  solution. 

4.  The  excess  of  Ka  in  the  first  aqueous  solution  is 
removed  by  adding  nitric  acid  until  effervescence  no  longer 
takes  place;  then  Ka  only  is  present  in  addition  to  the 
Sate,  which  in  no  way  can  interfere  with  the  testing  fpr 
that  Sate. 

5.  In  the  same  manner,  Ag  Mrate,  fluxed  with  Ka  Cate, 
yields  Ka  Mrate,  which  is  extracted  by  water,  together  with 
the  excess  of  Ka  Cate  taken.  The  residue  of  Ag  Cate,  in- 
soluble in  water,  is  readily  dissolved  by  dilute  nitric  acid, 
giving  Ag  Nate.  Thus  also  here,  the  acid  is  found  in  that 
portion  of  the  flux  soluble  in  water,  the  metal  in  that  portion 
insoluble  in  water,  but  soluble  in  acids. 

6.  SILICATES,  M Siates,  fluxed  in  the  same  manner,  give 
Ka  Siate  and  M Cate.  In  this  case,  the  entire  fluxed  mass  is 
treated  directly  with  dilute  muriatic  acid,  causing  the  effer- 
vescence of  fixed  air  and  the  separation  of  silicic  acid  in  the 
GELATINOUS  CONDITION.  Evaporating  to  dryness,  heating 
the  dry  residue  gently  till  all  acid  vapors  are  driven  off,  the 


FLUX  AND  GLASS. 


157 


metallic  muriates  will  be  taken  up  in  water,  while  SILICA  will 
remain,  being  insoluble. 

7.  In  general,  the  compound  insoluble  in  acids  may  be 
represented  by  M Rate,  where  M designates  the  metallic,  R the 
non -metallic  constituent.  Fusing  with  excess  of  Ka  Cate 
gives,  by  double  decomposition,  M Cate  (insol.)  and  Ka  Rate 
(sol.  in  water),  together  with  the  excess  of  Ka  Cate  not 
changed. 

As  a MIXTURE  of  Na  and  Ka  carbonates  is  much  more  fusi- 
ble than  either  carbonate  taken  singly,  the  mixture  is  preferred. 
Not  less  than  four  times  the  weight  of  the  substance  should 
be  taken. 

8.  In  some  cases,  it  is  advisable  to  add  other  fluxes  to  the 
carbonates  or  to  take  other  fluxes  instead;  but  the  process 
remains  essentially  the  same,  namely,  a double  decomposi- 
tion by  fusion. 

For  simple' TESTING,  it  suffices  to  fuse  a little  of  the  in- 
soluble substance  into  a soda  bead  on  the  platinum  loop. 

9.  The  silica  (6)  dissolves  readily  in  a soda  bead  on  fusion, 
under  lively  effervescence  of  fixed  air.  This  is  a very  simple 
test  for  silica.  With  enough  silica,  the  bead  remains  trans- 
parent when  cold;  in  fact,  a GLASS  has  been  formed.^  This 
glass  being  soluble  in  water,  is  called  SOLUBLE  GLASS.  It  is 
manufactured  in  quantity  for  various  applications. 

10.  Ordinary  GLASS,  not  soluble  in  water,  nor  in  acids,  is 
an  AMORPHOUS  DOUBLE  SILICATE  of  Na  and  Ca  (window 
glass)  or  Ka  and  Ca  (crown  glass).  Flint  glass  contains  also 
lead  silicate.  The  carbonates  mixed  in  proper  proportions 
with  silica,  when  fused  and  slowly  cooled,  give  true,  amorphous 
glass;  when  rapidly  cooled,  crystallization  may  take  place, 
resulting  in  an  opaque  mass — not  a real  glass. 

11.  The  quality  of  the  glass  produced  depends  on  the 
proportion  of  the  essential  materials  and  their  purity.  Common 


158 


LECTURE  27. 


bottles  have  to  be  very  cheap — hence  they  are  made  from 
lowest  grade  materials. 

COLORED  GLASS  is  obtained  by  small  additions  of  metallic 

calxes,  which  dissolve,  pro- 
ducing the  same  colors 
permanently  as  shown  in 
the  borax  bead  for  a short 
time  only.  The  Egyptians 
made  good  glass,  mainly 
colored ; the  cut  represents 
specimens  thereof.  Com- 
pare 5,  6. 

12.  SILICA,  being  absolutely  non-volatile  in  our  furnaces, 
drives  out  all  other  non -metallic  constituents  from  salts,  when 
heated  therewith;  for  these  non-metallic  constituents  are 
volatile,  and  thus  cannot  remain  at  such  temperatures.  Silica 
drives  out  all  other  constituents,  not  because  it  is  stronger,  or 
has  greater  affinity,  but  simply  because  it  cannot  get  away, 
while  the  others,  being  volatile,  can  escape  from  the  fiery 
furnace,  and  do  so. 


27.  METALS  AND  RADICALS. 

1.  Having  become  familiar  with  the  principal  chemical  pro- 
cesses and  a considerable  number  of  chemical  substances, 
both  native  and  artificial,  it  seems  advisable  to  recapitulate  a 
few  of  the  general  facts  in  order  to  find  the  best  way  forward 
in  the  study  of  chemistry. 

2.  First  of  all,  we  have  learned  to  distinguish  on  INDI- 
VIDUAL CHEMICAL  SUBSTANCE  from  all  sorts  of  mere  mix- 
tures. The  crystal  form,  specific  gravity,  fusing  and  boiling 
point,  and  other  properties,  give  as  many  criteria  for  the  recog- 
nition of  the  individual  chemical,  and  if  need  be,  as  many 


METALS  AND  RADICALS. 


159 


methods  of  separation  and  purification  expressed  by  the  gen- 
eral term  of  FRACTIONING. 

3.  In  this  manner  the  metals,  salts  and  acids  have  pre- 
sented themselves  as  CLASSES  or  FAMILIES  of  chemical 
individuals.  The  metals,  possessing  that  peculiar  luster 
(metallic)  and  malleability.  The  salts,  generally  crystallizing 
from  aqueous  solution  and  by  the  blowpipe  revealing  the 
presence  of  a metal.  The  acids,  dissolving  metals  under  the 
evolution  of  hydrogen  or  other  gases,  with  the  production  of 
salts. 

4.  The  study  of  the  solution  of  metals  in  dilute  acids  re- 
vealed the  fact,  that  acids  are  hydrogen  salts,  or  that  the 
hydrogen  in  the  acids  corresponds  to  the  metals  in  the  salts. 
Solution  of  a metal  in  an  acid  is  simply  a substitution  in  ab- 
solutely FIXED  PROPORTIONS  BY  WEIGHT,  termed  equiva- 
lents. These  are  referred  to  hydrogen  as  unit,  or  Mg  as 
twelve  (18,  10). 

5.  The  salts  and  acids  are  evidently  DUAL  BODIES,  con- 
sisting of  TWO  component  parts.  First,  the  metal  in  salts 
and  the  corresponding  hydrogen  in  acids.  This  component 
we  shall  call  the  METALLIC  CONSTITUENTS  of  salt  and 
acid;  for  hydrogen  is  metallic  in  its  character.  The  other 
constituent  is  NON-METALLIC,  the  salt  and  the  acids  re- 
sponding to  the  same  tests. 

6.  Thus,  a drop  of  sulphuric  acid,  added  to  an  acidified, 
dilute  solution  of  barium  nitrate,  produces  a white  precipitate; 
so  does  the  salt  obtained  by  dissolving  zinc  or  magnesium,  or 
any  other  metal,  in  sulphuric  acid.  All  these  chemicals  are 
therefore  SULPHATES,  namely  H S^te,  Zn  S^te,-]V\g  sate,  etc. 
Now  the  question  arises,  what  is  this  S^te? 

7.  We  have  abundant  evidence  that  this  S^te  is  volatile, 
and  we  can  prove  that  it  contains  sulphur,  both  by  SYNTHE- 
SIS and  by  ANALYSIS.  Burning  sulphur  in  a tube,  carrying 


160 


LECTURE  27. 


the  product  of  combustion  through  water,  that  water  will  soon 
give  the  reaction  of  sulphates  with  barium  solutions,  especially 
if  a shaving  moistened  with  concentrated  nitric  acid  is  placed 
in  the  course  of  the  gas  produced.  Simply  heating  green 
vitriol  in  a glass  tube,  the  odor  of  burning  sulphur  becomes 
manifest;  that  is,  the  green  vitriol  must  contain  sulphur. 

8.  But  we  also  know  that  the  non -metallic  is  not  sul- 
phur merely — for  we  have  obtained  copper  sulphide  by  syn- 
thesis (21.8)  and  found  it  entirely  different  from  blue  vitriol, 
which  is  a sulphate. 

Consequently  the  non -metallic  constituent  of  sulphates  con- 
sists of  sulphur  and  something  else;  it  is  a complex  material, 
called  a RADICAL.  is  the  radical  of  sulphates. 

9.  We  have  already  determined  the  equivalent  of  this  rad- 
ical, and  can  now  determine  the  equivalent  of  its  constituents. 
The  equivalent  of  sulphuric  acid  we  found  to  be  49;  but  if  H 

is  49,  the  radical  has  the  equivalent  48.  It  con- 
tains sulphur;  but  S=16,  leaves  for  the  unknown  part  of  the 
Sate  radical  the  equivalent  32. 

10.  In  a like  manner  we  have  found  the  equivalent  of  the 
radical  of  CARBONATES  to  be  Gate  30  (25.10).  We  know, 
by  synthesis  (16.9),  that  it  contains  carbon. 

NITRATES  of  all  kinds,  being  derived  from  nitre  (13.9)  or 
Ka  Nate,  contain  the  radical  Nate,  the  equivalent  of  which  is 
62.  The  radical  Mrate  (MURIATE)  has  the  equivalent  35.5, 
carried  from  common  salts  (18,  12).  The  exact  nature  of 
these  radicals  is  also  unknown. 

11.  But  while  the  composition  of  these  radicals  of  salts  and 
acids  is  unknown,  we  can  practically  answer  all  questions 
about  their  ordinary  reactions.  If  we  wish  to  know  how  much 
salt  is  required  to  precipitate  a given  amount  of  silver  nitrate, 
and  how  much  silver  muriate  will  be  obtained,  we  have  all  the 
data  required  in  the  equivalents.  Namely,  Ag  108,  N^te  62, 


METALS  AND  RADICALS. 


ICl 


Mrate  35.5,  Na  23.  Accordingly  170  Ag  requires  58.5  Na 
and  will  yield  143.5  Ag  Mr^te. 

12.  It  is  apparent  that  the  sulphides  (21)  and  iodides  (23) 
are  compounds  of  a different  order.  They  consist  of  only  two 
substances,  the  metal  and  the  non-metal,  S or  lo.  Such  com- 
pounds are  called  BINARIES  or  binary  compounds.  They  are 
named  aS  exemplified.  The  terminal  DE  (from  duo,  two) 
with  the  essential  part  of  the  name  of  the  non-metal  (SULPH- 
ur)  by  the  connecting  vowel  i. 


28.  CHEMICAL  REACTIONS. 

1.  The  principal  chemical  processes  have  been  shown 
and  employed  in  the  preceding  lessons.  It  will  be  advisable 
now  to  review  and  classify  them.  We  shall  find  that  but  very 
few  really  different  reactions  exist.  It  must  be  born  in  mind, 
that  chemists  designate  any  chemical  action  by  the  word 
REACTION. 

2.  Ordinarily,  a volatile  substance  and  high  temperature 
cannot  co-exist;  the  volatile  substance  will  escape.  Hence, 
when  water  or  other  volatile  liquids  are  present,  no  high  tem- 
perature can  be  employed.  Practically  speaking,  all  chemical 
operations  are  therefore  either  in  the  DRY  WAY  or  WET  WAY, 
according  as  high  temperatures  or  volatile  liquids  are  used. 

3.  But  if  the  volatile  liquid  be  enclosed  in  a vessel  strong 
enough  to  resist  the  rapidly  increasing  pressure  of  the  vapor 
from  within  as  well  as  the  high  temperature  applied  from 
without,  the  distinction  between  the  two  ways  will  become 
less  marked.  Since  such  vessels  usually  are  constructed  so  as 
to  close  themselves  more  tightly,  the  greater  the  pressure  of 
the  vapor,  they  are  termed  AUTOCLAVES.  The  first  auto- 
clave was  Papin’s  digestor. 


162 


LECTURE  28. 


4.  Work  with  the  auto- 
clave is  both  difficult  and 
dangerous.  The  old  chemists 
had  nothing  corresponding  to 
this,  and  modern  chemists 
have  restricted  its  use  mainly 
to  organic  chemistry.  In  its 
simplest  form,  the  autoclave 
is  a strong  glass  tube,  drawn 
out  and  closed  by  fusion,  after 
the  charge  has  been  intro- 
duced. Daubree  and  Friedel 
have  used  the  autoclave  in 
mineral  chemistry.  The  first 
obtained  fine  crystals  of  quartz 
and  pyroxene;  the  latter  ob- 
G.  A.  DAUBREE.  tained  feldspars  and  topaz 

Died  May  28,  1896,  at  the  age  of  82  years.  CryStalS  in  that  Way. 

5.  Only  THREE  really  different  classes  of  CHEMICAL 
REACTIONS  can  be  recognized,  namely  synthesis,  substitution 
and  double  decomposition.  In  synthesis,  two  substances 
unite  to  form  a new  compound.  In  substitution,  a substance 
takes  the  place  of  one  of  the  two  constituents  of  a compound. 
In  double  decomposition,  two  compounds  mutually  interchange 
their  constituents,  forming  two  new  compounds. 

6.  A number  of  SYNTHESES  have  been  presented  in  the 
preceding  lectures;  especially  the  formation  of  sulphides  (21) 
and  iodides  (23).  The  conditions  under  which  two  substances 
unite  must  be  specially  studied;  the  degree  of  temperature 
required  is  always  an  important  factor. 

The  opposite  of  synthesis  is  ANALYSIS,  the  term  taken  in 
its  broadest  sense  of  separation.  Such  reactions  will  soon 
come  before  us. 

7.  SUBSTITUTION  may  involve  the  metallic  or  the  non- 
metallic  constituent  of  a compound.  When  a metal  is  dis- 
solved in  dilute  acids  (17)  or  when  reduced  in  the  wet  way 


CHEMICAL  REACTIONS. 


1G3 


(18),  it  is  the  metallic  constituent  which  is  replaced.  When 
hydriodic  acid  is  formed  by  hydrogen  sulphide  (23,  5)  it  is 
the  non-metallic  constituent  that  is  replaced. 

8.  Of  DOUBLE  DECOMPOSITIONS  we  must  distinguish 
four  kinds,  namely  by  neutralization  (25,  3),  by  volatilization 
(22,  2),  by  precipitation  (22,  7),  and  by  fusion  (26,  2).  Of 
these  four,  the  first  is  erroneously  considered  a synthesis  of 
acid  and  base;  for  water  (H  H^te)  actually  forms,  as  well  as 
the  new  salt.  The  last  depends  largely  upon  an  excess  of 
the  flux. 

9.  In  the  case  of  precipitation,  it  is  clear  that  insoluble 
compounds  cannot  stay  in  solution;  hence  two  compounds, 
containing  separately  the  ingredients  of  an  insoluble  com- 
pound, will  produce  a precipitate  when  brought  together  in  the 
same  liquid.  This  rule  was  first  given  by  Berthollet  (p.  32). 
Accordingly,  if  an  insoluble  compound  is  to  be  prepared,  mix 
two  solutions,  the  one  containing  the  metal,  the  other  the 
radical  of  that  compound. 

10.  If  two  substances,  containing  the  constituents  of  a 
volatile  compound  are  exposed  to  a temperature  higher  than 
that  at  which  the  volatile  compound  boils,  it  cannot  remain 
and  will  pass  over  as  gas  or  vapor.  This  is  the  second  rule  of 
Berthollet. — H N^te  drives  out  at  common  temperature 
from  Ka  Side.  Xhe  Ka  N^te  remaining,  heated  on  a sandbath 
with  H S^te,  gives  a distillate  of  H N^te.  Xhe  Ka  S^te  remain- 
ing, heated  to  redness  with  silica,  gives  a residue  of  Ka  Si^te. 
The  S^te  decomposes  as  it  is  driven  off. 

11.  It  is  therefore  of  the  highest  importance  to  know  the 
VOLATILITY  and  SOLUBILITY  of  compounds,  in  order  to 
understand  chemical  tests  and  the  methods  of  preparation  of 
chemicals.  The  rules  of  Berthollet  then  will  be  the  most 
valuable  guides.  For  example,  let  Ba  S^te  be  wanted.  Being 
quite  insoluble,  it  will  form  as  precipitate  if  to  ANY  Ba  Solu- 
tion we  add  the  solution  of  ANY  sulphate.  Therefore,  take 
the  common  Ba  Mr^te  and  add  H S^te^  and  Ba  S^te  ^^\\\  pre- 
cipitate. 


164 


LECTURE  29. 


12.  These  RULES  OF  BERTHOLLET  (p.  32)  even  apply 
to  cases  merely  difficultly  soluble.  For  example,  by  the  Gay- 
Lussac  lines  of  solubility  (p.  70),  it  appears  that  the  solubility 
of  nitre  rapidly  increases  with  temperature,  much  more  so  than 
that  of  Chili  saltpeter,  while  salt  (Na  Mr^te)  hardly  increases 
in  solubility.  Accordingly,  the  high  priced  Ka  is  made 
(by  conversion)  by  dissolving  the  cheap  Stassfurth  Ka  Mr^te 
(Ka  Clide  on  Chart)  in  boiling  water,  and  adding  cheap  Chili 
saltpeter;  common  salt  will  separate,  and  from  the  hot  solu- 
tion nitre  will  crystallize  on  cooling. 


Note. — Diagrams  of  Reactions  should  be  written  out  in  the  sim- 
plest possible  manner.  The  essential  features  of  the  reactions  should  be 
specially  marked,  namely  insolubility,  volatility,  etc.  The  substances 
actually  taken  are  written  one  above  the  other;  the  determining  reac- 
tion is  now  marked  by  one  heavy  line  terminating  in  an  arrow,  and  the 
CONSEQUENT  REACTION  is  marked  by  a light  double  line.  For  gases  and 
vapors,  the  line  should  be  drawn  upwards;  for  precipitates  the  line 
should  be  drawn  downwards,  as  shown  in  the  few  instances  here  given. 
The  diagram  represents  four  characteristic  cases,  and  needs  no  further 
explanation.  The  student  should  acquire  the  habit  of  writing  out  every 
reaction  in  this  manner. 

Complex  Reactions  are  simply  two  or  more  of  the  simple  reactions 
described,  succeeding  one  another  at  shorter  or  longer  intervals  of  time. 
As  an  example,  the  gradual  change  of  Ka  Side  to  Ka  S^te  is  shown  in  the 
diagram. 


29.  COMBUSTION  AND  PHLOGISTON. 

1.  The  heat  of  the  sun  gives  motion  to  all  things  on  this 
globe.  Without  the  central  luminary,  no  life  could  exist  on 
the  earth.  When  man  succeeded  to  make  a fire  for  his  own 
use,  he  took  the  greatest  step  towards  civilization.  The 
Greek  myth  of  Prometheus  voices'  the  recollection  of  the  race. 

2.  In  science,  both  physical  and  chemical,  heat  and  light 
occupy  an  equally  prominent  place.  In  chemistry,  heat  is  one 
of  our  principal  powers  for  effecting  changes  of  matter.  The 
operations  in  the  dry  way  range  from  blowpipe  tests  to  the 


COMBUSTION  AND  PHLOGISTON. 


165 


smelting  of  iron  and  glass  in  gigantic  furnaces.  Modern 
progress  largely  is  brought  about  by  the  use  of  our  mineral 
combustible,  coal  giving  both  heat  and  power. 

3.  The  phenomenon  of  combustion  itself  is  one  of  the 
greatest  questions  in  chemical  science.  As  the  sun  seems  to 
rise  in  the  east  of  the  observer,  himself  at  rest  in  the  restful 
landsc^^pe,  so  the  combustible  when  burning  seems  to  set  free 
heat  in  flame  (phlox  or  phlogion)  and  glow,  leaving  behind 
but  a little  of  ashes  or  calx.  The  main  part  of  the  combust- 
ible seems  to  be  PHLOGISTON. 

4.  But  long  continued  and  most  careful  observation  of  the 
stars  finally  convinced  COPERNICUS  that  it  is  the  sun  which 
is  at  rest,  and  not  the  earth.  In  a like  manner,  LAVOISIER  has 
demonstrated,  that  the  combustible  does  not  diminish,  but 
greatly  increase  in  weight  during  the  process  of  combustion. 
Lavoisier  is  the  Copernicus  of  chemistry. 

5.  These  general  reflexions  form  a necessary  introduction 
to  the  chemical  study  of  combustion,  which  we  now  will  enter 
upon.  It  will  soon  become  apparent  that  this  term  cannot 
be  restricted  to  flame  and  fire,  but  applies  equally  to  phenom- 
ena of  world  wide  extent,  but  so  slow  and  so  wide  diffused, 
that  neither  flame  nor  visible  glow  attend  them. 

6.  It  was  the  German  chemist  GEORG  ERNST  STAHL 
(1660-1734)  who  first  (1697  and  especially  1717)  grouped  all 
phenomena  of  combustion  and  tried  to  explain  them  by  the 
hypothesis  of  phlogiston.  All  combustible  materials  were 
supposed  to  contain'  phlogiston;  wood,  oil,  fat,  wool,  also  grain 
and  of  mineral  materials,  metals,  coal  and  especially  sulphur. 

7.  According  to  this  theory,  the  metals  are  compounds  of 
the  metallic  calx  and  phlogiston.  Heating  metallic  lead  before 
the  blowpipe,  it  burns,  that  is,  phlogiston  is  set  free;  the  calx 
remaining  as  incrustation  on  the  charcoal,  is  simply  the  other 
constituent  of  the  metal. 

8.  Now  metals  are  more  or  less  readily  calcinated,  that  is, 
more  or  less  combustible,  as  has  been  exemplified  in  the 


166 


LECTURE  30. 


seventh  lecture.  Charcoal  is  much  more  combustible  than 
any  of  the  common  (heavy)  metals.  This  is  evident  because 
we  can  burn  all  kinds  of  coal  in  an  iron  stove  without  con- 
suming the  iron. 

9.  In  the  phlogiston  theory  of  Stahl,  the  metal  must  con- 
tain less  phlogiston  than  coal.  Consequently,  when  metallic 
calxes,  intimately  mixed  with  carbon,  are  heated,  the  carbon 
transfers  its  phlogiston  to  the  metallic  calx.  The  metal  (calx 
and  phlogiston)  is  reproduced. 

10.  But  this  phlogiston  which  is  supposed  to  readily  leave 
carbon  and  unite  with  the  calx  to  form  the  metal,  was  never 
produced  in  the  free  state;  and  when  weighed  amounts  of 
metals,  like  tin,  were  calcined,  they  notably  increased  in 
weight,  as  already  shown  by  Jean  Rey,  a pharmacist  of  Ber- 
gerac, in  1629. 

11.  When  hydrogen  gas  had  been  discovered  by  Caven- 
dish, it  was  supposed  to  be  phlogiston,  or  the  fire -matter  of 
Stahl.  Cavendish  himself  remained  a defender  of  the  phlogis- 
ton theory  till  his  death  (1810). 

12.  For  nearly  a century  this  phlogiston  theory  reigned 
supreme.  The  apparently  conflicting  facts  were  not  recog- 
nized. Within  a very  wide  circle  of  facts,  the  theory  seemed 
to  explain  everything  satisfactorily.  Like  the  Ptolemaic  sys- 
tem of  the  world,  it  was  considered  to  be  in  strict  accordance 
with  the  everyday  testimony  of  the  senses.  To  doubt  it  was 
almost  a crime,  especially  in  Germany. 


30.  COMBUSTION  AND  OXYGEN. 

1.  It  would  be  very  interesting  to  study  the  history  of 
the  CHEMICAL  REVOLUTION  (Berthelot)  which  marked  the 
last  quarter  of  the  eighteenth  century,  but  time  forbids.  It 
will  be  necessary  to  confine  ourselves  to  the  most  conclusive 
experiments,  independent  of  their  historic  order. 


COMBUSTION  AND  OXYGEN. 


1G7 


2.  A weighed  piece  of  magnesium  wire,  burnt  over  a 
weighed  dish,  will  show  quite  a large  INCREASE  IN  WEIGHT, 
though  the  violence  of  the  combustion  makes  a partial  loss  of 
the  calx  unavoidable.  Under  most  favorable  circumstances, 
this  increase  in  weight  is  about  two-thirds  of  the  weight  of  the 
metal  taken. 

3.  IN  THE  WET  WAY  the  calx  of  a metal  may  be  obtained 
by  dissolving  the  metal  in  nitric  acid,  evaporating  and  igniting; 
the  residue  is  the  calx.  Such  determinations  have  been  made 
by  Berzelius  (p.  22).  Lead  increased  almost  8 per  cent.,  mer- 
cury fully  as  much,  and  copper  25  per  cent.  There  can  be  no 
doubt  about  the  increase  in  weight  in  calcination. 


4.  Lead  converted  into  nitrate  gains  60  per  cent.  (19,  12). 

Igniting  the  nitrate  in  a 
tube,  rutilant  vapors  first 
appear  in  abundance, 
then  a colorless  gas;  a 
shaving  with  but  a single 
glowing  point,  will  burst 
into  flame  when  held  in 
this  gas.  Priestley  made 
this  experiment  1772; 
the  gas  he  called  “de- 
phlogisticated  air.”  Its 
main  character  is  that 
it  SUPPORTS  COMBUS- 
TION. 

5.  Mercury  heated  for 
a long  time  steadily  to 
near  its  boiling  point  is 
slowly  converted,  espec- 
ially on  the  surface,  into 
PRIESTLEY  STATUE.  a RED  crystalline  pow- 

der, called  “precipitate  per  se”  also  simply  RED  PRECIPI- 
TATE. It  is  the  calx  of  mercury.  In  the  wet  way  it  is  pre- 
pared much  more  rapidly,  in  the  manner  above  stated  (3). 


168 


LECTURE  30. 


. 6.  Heating  this  red  precipitate  in  a tube,  it  first  turns  dark 
brown,  then  drops  of  metallic  mercury  appear  on  the  cold  parts 
of  the  tube.  At  the  same  time  a colorless  gas  is  evolved,  the 
amount  of  which  may  be  measured  by  our  gas  burette. 
Tested  as  above  stated,  it  supports  combustion,  or  is  dephlo- 
gisticated  air.  Lavoisier,  who  made  the  same  experiments 
soon  after,  finally  called  this  gas  OXYGEN.  Scheele  had 
called  it  fire  air. 

7.  OXYGEN  GAS,  collected  in  the  usual  way,  is  shown  to 
be  colorless,  odorless,  energetically  supporting  combustion; 
it  is  slightly  heavier  than  atmospheric  air. 

It  was  first  liquefied  in  1877,  by  Cailletet  and  Pictet;  its 
critical  point  is  at  118  degs.  below  zero;  50  atmospheres  pres- 
sure liquefies  it  at  that  temperature. 

8.  Oxygen  is  most  readily  OBTAINED  IN  QUANTITY  by 
moderately  heating^  the  salt  known  as  potassium  chlorate, 
which  crystallizes  in  thin  (oblique)  rhombic  tablets  of  104.4 
degs.  This  salt  first  fuses,  then  decomposes,  often  with  ex- 
plosive violence.  When  it  is  mixed  with  pulverized  pyrolusite 
(9,  7),  the  decomposition  begins  at  a lower  temperature  and  is 
entirely  safe  and  without  violence. 

9.  COMBUSTIONS  in  oxygen  gas  are  most  beautiful  and 
instructive,  if  performed  in  combustion  tubing  of  hard  glass, 
connected  through  the  drying  columns  with  the  generator,  and 
on  the  other  end  with  suitable  absorption  flasks  for  the  pro- 
ducts of  combustion.  Some  of  the  substances  to  be  burnt  are 
better  placed  in  porcelain  boats.  This  method  of  experimen- 
tation is  under  perfect  control  of  the  operator,  and  much 
more  instructive  to  the  student,  than  the  common  way  witl4 
large  flasks. 

10.  CARBON  (small  prisms  of  blowpipe  charcoal)  burns 
with  a brilliant  white  light;  the  product  is  fixed  air  (16). 
SULPHUR  burns  with  a blue  flame;  the  product  is  a gas,^ 
bleaching  blue  litmus  after  having  turned  it  red.  PHOS- 
PHORUS burns  with  flame,  emitting  a most  dazzling  white 


COMBUSTION  AND  OXYGEN. 


109 


light  and  giving  a solid,  white  product  of  combustion,  which 
dissolves  in  water,  to  an  acid  (phosphoric).  MAGNESIUM 
and  ZINC  burn  also  with  brilliancy — the  first  giving  white,  the 
second  green  light.  SODIUM  burns  with  dazzling  yellow  light. 

11.  Several  of  these  combustions  can  be  shown  to  still 
greater  advantage  by  using  the  COMPOUND  BLOWPIPE  (5,9), 
connecting  the  inner  tube  with  the  oxygen  supply.  STEEL 
watch  springs  burn  in  this  flame,  producing  a magnificent 
shower  of  brilliant  sparks  of  burning  steel.  PLATINUM  wire 
melts  readily  in  this  oxy-gas  flame.  LIME  emits  a most  dazz- 
ling white  light  when  held  in  this  flame;  this  is  the  so-called 
calcium  light. 

12.  Priestley  discovered  “ dephlogisticated  air”  1774 

in  England.  SCHEELE  pro- 
duced, entirely  indepen- 
dently, at  about  the  same 
time,  his  “fire-air”  in 
Sweden.  Both  remained 
firm  believers  in  the  phlo- 
giston theory,  although 
they  had  produced  the 
“eminently  respirable  gas” 
of  LAVOISIER,  which  he 
afterwards  called  oxygen. 
Too  ofte*n,  modern  science 
forgets  this  lesson ; thought 
is  as  important  as  fact. 
The  old  “ora  et  labora  ” 

scientists  should  read,  “think  and  work.” 


SCHEELE. 


Notes  8.  Oxygen  gas  need  not  be  collected  in  bag  or  gasometer 
beforehand;  it  may  be  generated  while  the  experiments  in  combustion 
(9)  are  exhibited  to  the  class.  , 

In  the  DRY  WAY,  it  is  most  elegantly  generated  by  filling  the  mixture 
of  chlorate  and  pyrolusite  (black  oxide  of  manganese)  in  a combustion 


170 


LECTURE  30. 


tube  and  heating  this  in  the  combustion  furnace.  By  properly  regula- 
ting the  gas  flames  as  to  size  and  number^  the  flow  of  oxygen  can  easily 
be  kept  exactly  as  wanted.  The  gas  should  be  dried  in  columns,  and 
passed  through  a little  concentrated  sulphuric  acid  in  a wash  bottle  (with 
straight  safety  tube)  before  it  reaches  the  tube  in  which  the  combustion 
is  effected.  The  mixture  should  be  dry,  fill  the  entire  length  of  the  com- 
bustion tube,  but  only  about  two  thirds  of  its  width.  The  heating  should 
begin  nearest  the  drying  columns.  The  total  amount  of  oxygen  for  all 
combustions  is  very  small,  when  they  are  made  as  stated  in  the  text,  in 
combustion  tubing  of  about  one  inch  diameter.  Th6  wash  bottle  with 
concentrated  sulphuric  acid  is  mainly  inserted  to  show  the  rate  at  which 
the  gas  flows. 

In  the  WET  WAY,  oxygen  is  generated  during  my  lectures  exactly  as 
hydrogen.  The  Kipp  is  charged  with  lumps  of  pyrolusite  and  commer- 
cial (lo  volume)  peroxide  of  hydrogen  to  which,  cautiously  and  in  small 
doses,  about  one  twelfth  volume  of  concentrated  sulphuric  acid  has  been 
added.  This  process  is  perfect;  of  course,  the  gas  is  rather  expensive 
when  obtained  in  this  way.  It  is  readily  understood  that  the  volume, 
is  about  twenty  times  that  of  the  liquid  reagent  used. 

The  generating  liquid  must  be  drawn  off  at  the  close  of  the  hour  or 
day;  it  deteriorates  in  keeping. 

9.  The  combustion  of  the  sodium  is  most  brilliant  and  most  conveni- 
ently performed  in  an  iron  deflagrating  spoon ; light  the  metal  (thor- 
oughly freed  from  the  naphtha)  by  the  flame  of  a Bunsen  burner,  then 
direct  a jet  of  oxygen  gas  upon  it  by  means  of  a glass  tube.  For  obvious 
reasons  it  is  advisable  that  the  experimentator  wear  a mask  or  watch  the 
combustion  through  a pane  of  blue  glass  larger  than  the  face. 

The  form  of  experimentation  described  in  the  books  is  much  less 
brilliant  in  results,  comparatively  clumsy  and  wasteful,  and  finally  much 
less  instructive. 

The  sodium  oxide  produced  contains  enough  peroxide  to  give  the  per- 
oxide of  hydrogen  reactions  when  dissolved  in  water. 

II.  When  time  and  means  allow,  the  oxy-hydrogex  blowpipe 
should  be  used,  and  the  most  striking  experiments  indicated  above, 
should  be  repeated.  In  this  case,  the  substances  may  be  most  conveni- 
ently supported  on  charcoal  or  cupels,  which  again  may  stand  on  a Bat- 
tersea scorifier  supported  on  the  ring  stand. 

29,  4.  That  Lavoisier  is  the  Copernicus  of  Chemistry  was  first  brought 
out  in  the  French  Resume  of  my  Atomechanik,  1867. 


31.  OXIDE  AND  RADICAL. 


1.  The  compounds  which  form  when  metals  burn  are  now 
understood  to  be  OXIDES,  consisting  of  the  metal  and  oxygen. 
All  metallic  calxes,  made  by  heating  the  metal  in  air,  must  be 
oxides;  in  other  words,  oxygen  must  be  a constituent  part  of 
atmospheric  air.  This  was  demonstrated  by  LAVOISIER,  as 
shall  be  shown  in  the  next  lecture  (see  Frontispiece). 

2.  The  metallic  calxes  prepared  in  the  wet  way,  being 
identical  with  those  obtained  in  the  dry  way,  therefore  also 
are  oxides.  Accordingly,  the  determinations  made  by  Berzelius 
(30,  3)  are  really  determinations  of  the  equivalent  of  oxygen. 
If  mercury  (equiv.  100)  increases  8 per  cent,  the  equivalent 
of  the  oxygen  is  8.  Copper,  having  an  equivalent  of  almost 
32,  increases  25  per  cent.,  that  is  8,  which  is  the  equivalent 
of  the  substance  combined  with  copper,  or  the  oxygen. 

3.  SYNTHESIS  OF  WATER.  Water,  forming  in  the  com- 
bustion of  hydrogen  gas  (17,  8),  therefore  is  hydrogen  oxide. 
The  exact  proportions  by  weight  of  oxygen  and  hydrogen  in 
water  were  first  determined  in  1841  by  DUMAS  (p.  25).  The 
hydrogen  was  carefully  purified  and  dried  (17,  5),  passed  over' 
copper  oxide  in  a combustion  TUBE  resting  on  tiles  barely 
glowing  red;  water  forms,  condensing  in  the  GLOBE  to  a 
liquid;  to  avoid  the  escape  of  traces  as  vapor,  the  globe  is 
followed  by  a light  absorption  tube.  The  black  copper  oxide 
is  gradually  turning  red,  being  reduced  to  metallic  copper. 

4.  This  is  not  the  place  for  a discussion  of  the  details  of 
this  determination  of  one  of  the  fundamental  data  of  chemical 
science.  Such  a discussion  the  author  has  published,  1894,  in 
his  True'  Atomic  Weights,  pp.  176-183.  The  errors  involved 
in  more  recent  determinations  by  chemists  using  more  elabo- 
rate and  complex  processes  have  also  been  indicated  (pp. 
185-189). 


172 


LECTURE  31. 


5.  The  weight  of  the  combustion  tube  with  copper  oxide, 
diminished  by  the  weight  of  the  same  tubes  at  the  close  of  the 
operation,  when  the  black  oxide  has  been  reduced  to  metallic 
copper,  evidently  gives  the  weight  of  the  oxygen  consumed  to 
form  the  water.  The  weight  of  the  water  formed  is  the  in- 
crease in  weight  of  the  globe  and  absorption  tube.  In  all 
experiments  the  proportion  of  the  weight  of  the  oxygen  to  that 
of  the  water  is  found  as  8 to  9 exactly.  Hence  the  hydrogen 
used  weighed  one.  Consequently,  the  equivalent  of  oxygen 
is  8,  exactly. 

6.  A CHEMICAL  FORMULA  (IN  EQUIVALENTS)  REPRE- 
SENTS ONE  EQUIVALENT  OF  THE  COMPOUND  BY  THE 
SYMBOLS  OF  THE  EQUIVALENTS  OF  THE  COMPONENTS. 
The  symbols,  when  representing  an  equivalent,  we  shall  print 
in  italics. 

Thus,  the  chemical  formula  of  water  is  HO.  This  formula 
expresses  the  simple  FACT  that  one  equivalent  of  hydrogen, 
H—\^  and  one  equivalent  of  oxygen,  C=8,  are  contained  in 
one  equivalent  of  water  HO=d, 

7.  DUMAS  (p.  25)  also  established  the  true  equivalent  of 
carbon,  by  burning  a weighed  amount  of  diamond  in  a current 
of  pure  oxygen  gas,  and  weighing  the  amount  of  fixed  air  pro- 
duced, collected  in  strong  potassium  hydrate  solution  contained 
in  proper  absorption  tubes.  The  details  are  found  in  the 
author’s  True  Atomic  Weights,  pp.  19-24,  p.  147,  and  pp.  176- 
177.  The  weight  of  the  carbon  burnt  is  to  the  oxygen  taken 
up  as  3 to  8 exactly. 

8.  Accordingly,  the  equivalent  of  carbon  in  fixed  air  would 
be  3,  and  the  chemical  formula  of  fixed  air  would  be  CO. 
But  Chemists  have  assumed  for  reasons  that  need  not  be 
stated  here,  that  there  are  two  equivalents  of  oxygen  ( = 16)  in 
fixed  air  to  one  of  carbon.  The  experimental  proportion  of  8 
to  3 then  compels  the  adoption  of  6 as  the  equivalent  of  carbon 
and  the  formula  of  fixed  air  becomes  CO^.  For  that  reason 
fixed  air  is  commonly  called  CARBON  DIOXIDE. 


OXIDE  AND  RADICAL. 


173 


9.  We  can  now  establish  the  composition  of  THE  RADI- 
CALS in  carbonates  and  sulphates.  The  radical  S^te  (27,  9) 
has  the  equivalent  48.  Direct  experiments  have  shown  that 
it  contains  but  one  equivalent  of  sulphur,  16;  hence  the 
oxygen  weighs  32,  representing  four  equivalents.  Conse- 
quently the  equivalent  formula  of  the  radical  is  O^S. 
Sulphuric  acid  has  the  formula  ^ O^S.  The  following  formula 
represents  an  equivalent  each:  Wa  O^S.  — Cu  O^S.  — 
Pb  O^S.—  Ag  O^S. 

10.  Direct  experiments  of  this  kind  were  made  by  v. 
HAUER,  1857.  Heating  a weighed  amount  of  cadmium  sul- 
phate in  a current  of  dry  hydrogen  sulphide  gas,  he  obtained 
a residue  of  sulphide  weighing  69.23  per  cent,  of  the  sulphate 
taken.  Nine  careful  determinations  were  made.  Now,  since 
the  equivalent  of  Cd  is  56,  that  of  S 16,  Cd  is  72,  and 
Cd  O^S  should  be  104.  But  72  is  exactly  69.23  per  cent,  of 
104.  The  formula  of  is  therefore  correct. 

11.  The  radical  of  carbonates  was  found  to  have  the 
equivalent  30  (27,  10).  It  contains  only  one  carbon,  there- 
fore three  of  oxygen,  or  C^te  is  O^C. 

For  magnesium  carbonate  Mg  OgCthis  gives  42.  Ignition 
leaves  the  oxide.  Mg  0=20  or  47.62  per  cent.  Actual  deter- 
minations made  by  SCHEERER  in  1850  on  Magnesite  from 
Frankenstein  gave  47.63  per  cent.,  thus  confirming  the  above. 

12.  For  carbonates  and  sulphates  the  radicals  are  now 
known.  The  third  constituent  has  been  found  to  be  oxygen. 
Its  equivalent  is  8,  that  of  hydrogen  being  one.  In  carbon- 
ates enter  three  equivalents  of  oxygen  with  the  equivalent  of 
the  metal  and  the  carbon.  In  sulphates  there  are  four  equiva- 
lents of  oxygen. 

The  radicals  of  nitrates  and  muriates  we  must  leave  unde- 
termined for  a short  time. 


32.  ANALYSIS  OF  THE  AIR. 


1.  The  terraqueous  globe  is  completely  surrounded  by  the 
air  as  by  a mantle,  protecting  us  equally  agaist  the  cold  of 
cosmical  space  and  the  burning  heat  of  the  sun.  In  this  air- 
mantle  float  the  clouds,  the  vapors  sent  up  from  the  earth  and 
sea  by  the  sunbeam ; they  descend  again  as  rain  and  snow. 
Into  this  air- mantle  passes  dust  and  smoke  from  factory  and 
fire.  Therefore,  we  call  it  with  the  Greeks,  the  ATMOS- 
PHERE. 

2.  AQUEOUS  VAPOR  is  present  in  the  air  in  greatly  vary- 
ing proportions.  We  are  sensitive  to  both  an  excessive 
amount  and  to  a deficiency  thereof.  Air  at  any  given  tem- 
perature can  contain  a definite  amount  of  vapor  only;  it  then 
is  saturated,  and  a good  HAIR  HYDROMETER  indicates  100  per 
cent,  moisture.  During  certain  southwest  winds  in  summer, 
the  humidity  of  the  air  may  run  down  to  less  than  10  per  cent; 
moving  air  of  this  character  (dry  winds)  scorches  vegetation. 

3.  In  these  United  States,  about  two  hundred  million  tons 
of  coal — worth  two  hundred  million  dollars — are  taken  from 
the  mines  and  burnt  every  year  (12.10),  returning  something 
like  530  million  tons  of  fixed  air  to  our  atmosphere,  together 
with  smoke  and  ashes.  Animal  life,  in  the  act  of  respiration, 
also  sends  enormous  quantities  of  fixed  air  into  the  atmos- 
phere. Plants,  we  shall  learn,  take  up  this  gas,  decompose 
it  by  the  aid  of  the  sunbeam,  and  thus  maintain  a sort  of 
equilibrium. 

4.  The  chemical  examination  of  atmospheric  air  must, 
therefore,  begin  with  the  determination  of  the  amounts  of 
moisture  (water)  and  fixed  air  (carbon  dioxide)  present  in 
the  same.  Effective  absorbents  (17,  5,  6),  contained  in  light 
glass  vessels  of  suitable  form  for  accurate  weighing,  will  re- 
tain these  separately.  The  increase  in  weight  of  these  ves- 
sels will  tell  the  amount  of  water  and  carbon  dioxide  in  the 
volume  of  air  that  has  passed  through  them. 


ANALYSIS  OF  THE  AIR. 


175 


5.  The  simplest  means  of  drawing  air  through  a series  of 
vessels  is  by  means  of  the  ASPIRATOR.  Any  flask  or  jug 
may  be  used  as  such,  if  closed  with  a doubly  perforated  stop- 
per, provided  with  siphon,  reaching  to  near  the  bottom  of  the 
flask  and  lengthened  by  rubber  tube  outside,  while  the  other 
perforation  by  means  of  a short  tube  connects  with  the  set  of 
absorption  vessels.  The  volume  of  the  water  flown  out  is 
equal  to  the  volume  of  air  drawn  through.  Special  aspirator 
flasks,  with  a lower  side-tubulature,  are  in  the  market. 

6.  As  a rule,  the  moisture  is  absorbed  by  fragments  of 
pumice,  soaked  with  concentrated  sulphuric  acid,  and  kept  in 
so-called  U-TUBES,  now  elegantly  made  with  ground  glass 
stoppers  and  with  short  glass  tubes  for  making  connection. 
The  carbon  dioxide  is  absorbed  by  a strong  solution  of  caustic 
potassa,  contained  in  some  of  the  varied  forms  of  POTASSA 
BULBS,  first  introduced  by  Liebig  (p.  23).  Further  details 
belong  to  practical  chemistry. 

7.  Such  determinations  have  shown  that  the  amount  of 
water  varies  enormously,  as  was  anticipated ; they  have  also 
shown  the  entirely  unexpected  fact,  that  the  amount  of  car- 
bon dioxide  varies  but  very  little  in  the  atmosphere.  In  round 
numbers  it  amounts  to  three  volumes  in  ten  thousand  volumes 
of  air. 


8.  Pure  and  dry  atmospheric  air  can  be  obtained  by  draw- 
ing common  air  through  a set  of  absorption  tubes  of  suitable 
size,  to  the  vessel  where  the  air  is  to  be  used.  See  17,  6. 
If  necessary  to  exclude  all  moisture  and  carbon  dioxide,  a 
TEST  SET  of  U and  bulb  tubes,  inserted  between  the  absorp- 
tion columns  and  the  receiver,  must  show  no  increase  in  weight. 

9.  If  now  a measured  volume,  say  100  cc,  of  such  pure  air 
be  slowly  passed  over  pure  copper  gauze,  heated  to  a low 
redness  in  a combustion  tube,  connected  with  a strong  glass 
receiver,  which  as  well  as  the  tube  with  copper,  was  com- 
pletely evacuated  by  a mercurial  air  pump,  the  copper  will 
turn  black,  combining  with  the  oxygen  of  the  air.  The  resi- 


176 


LECTURE  32. 


dual  air  measures  79  cc,  so  that  21  cc  were  oxygen.  Dumas 
(p.  25)  and  Boussingault. 

10.  This  residual  air  is  colorless  and  odorless;  it  does  not 
support  combustion  nor  life.  For  the  latter  reason,  Lavoisier 
called  it  AZOTE  and  many  French  chemists  continue  to  use 
the  symbol  Az  for  this  gas.  We  call  it  NITROGEN,  and  repre- 
sent by  the  symbol  N.  Careful  weighings  have  shown  it  to  be 
lighter  than  oxygen,  in  the  proportion  7 to  8.  Nitrogen  has 
been  liquefied.  Its  critical  temperature  is  — 146  degrees,  its 
critical  pressure  35  atmospheres. 

11.  The  first  decisive  demonstration  of  the  composition  of 
atmospheric  air  was  made  by  Lavoisier.  Our  frontispiece 
pictorially  commemorates  this  great  event.  Mercury  was  kept 
near  its  boiling  point  for  twelve  days  and  nights  continuously; 
then  the  red  precipitate  first  formed  no  longer  showed  increase, 
nor  the  volume  of  air  any  decrease. 

After  cooling,  the  residual  air  measured  42  to  43  cubic 
inches;  originally  50  cubic  inches  had  been  taken.  This 
shows  a reduction  of  about  15  per  cent  in  the  volume  of  air. 
The  residual  air  proved  to  be  azote. 

12.  The  red  precipitate  formed  weighed  45  grains.  Heated, 
it  left  41.5  grains  of  metallic  mercury,  yielding  7 to  8 cubic 
inches  of  gas,  proving  to  be  oxygen. 

When,  in  other  experiments,  the  amount  of  oxygen  so  ex- 
tracted by  mercury  and  set  free  again  from  the  red  precipitate, 
was  mixed  with  the  inert  residual  air  (nitrogen),  the  gas 
MIXTURE  resulting  was  in  every  way  identical  with  atmos- 
pheric air. 

This  completed  the  analysis  and  synthesis  of  atmospheric  air. 


Note.  The  discovery  of  dephlogisticated  air  by  Priestley  gave 
chemists  a new  gas  of  wonderful  properties,  only  to  involve  chemical 
processes  into  greater  contusion  and  deeper  mystery.  The  fire  air,  dis- 
covered independently  by  Scheele,  brought  some  light  into  the  chem- 
istry of  the  air,  but  most  of  the  processes  employed  by  him  were  so 
indefinite  as  to  make  it  difficult  even  to-day  to  express  them  in  formulai. 


LAVOISIER. 


1794. 


ANALYSIS  OF  THE  AIR. 


177 


It  is,  therefore,  natural,  that  both  Priestley  and  Scheele  remained 
faithful  to  the  phlogiston  theory,  according  to  which  metals  lose  some- 
thing (phlogiston)  when  calcinated  (dephlogisticated). 

Lavoisier,  the  Copernicus  of  chemistry,  pierced  the  veil  of  pheno- 
mena that  had  hidden  the  truth  to  all  previous  investigators,  lie  had 
only  the  same  facts  and  materials  which  were  also  in  the  hands  of  the 
English  and  Swedish  chemists,  who  both  were  most  eminent  investiga- 
tors of  the  empiric  or  purely  experimental  school. 

Lavoisier  as  an  experimentor  was  not  superior  to  Priestley  or  Scheele. 
It  is  true  he  possessed  unlimited  means  to  obtain  all  appliances  he  might 
desire;  but  his  brilliant  discoveries,  so  far  as  apparatus  was  concerned, 
might  have  been  made  equally  as  well  by  the  poor  apothecary  of  Koep- 
ing.  Surely,  there  never  was  a chemist  who  was  so  entirely  independent 
of  pecuniary  means  as  Scheele,  whose  very  mind  seemed  to  create  all 
the  appliances  he  needed.  Priestley  also  was  very  successful  in  doing 
much  with  little.  His  own  claims  of  having  made  his  discoveries  acci- 
dentally, is  one  of  the  oddities  of  his  character;  for  his  writings  bear 
witness  that  he  planned  his  experiments  carefully. 

Lavoisier  was  not  a specialist;  he  was  not  merely  an  experimentor,  for 
he  was  also  a profound  thinker.  His  studies  ranged  from  mathematics  to 
geology  and  physiology.  He  had  mastered  the  fundamental  and  essential 
parts  of  the  science  of  his  day,  as  did  the  great  philosophers  of  old.  To 
this  he  added  the  Especial  research  in  the  more  limited  field  of  the 
chemical  processes.  His  mind  directed  the  work  of  his  fingers;  and 
when  in  this  manner,  any  fold  of  the  veil  of  appearances  was  displaced, 
his  mind  was  able  to  read  the  new  form  in  accordance  with  the  eternal 
ideal. 

In  this  way  the  material  gathered  by  the  skillful  workmen  anywhere, 
in  England  or  in  Sweden,  were  refined  and  perfected  in  his  hand  and 
placed  by  his  mind  in  harmony  with  the  universal  laws  of  nature,  suffi- 
ciently so  to  find  the  eye  point  of  the  grand  perspective;  and  so  a revo- 
lution in  chemistry  was  accomplished,  exactly  corresponding  to  that 
effected  by  Copernicus  in  astronomy  two  and  a half  centuries  earlier. 

The  sun  and  the  stars  move  around  the  earth,  resting  in  the  center  of 
the  world ; so  the  senses  declared  before  Copernicus,  so  they  do  to  us. 
But  Copernicus  mentally  placing  his  eye  in  the  sun,  saw  clearly  the  true 
system  of  the  w’orld,  and  we  now  understand  the  mocking  of  our  senses. 

In  a fire,  the  wood  is  consumed,  the  flame  seems  but  a part  of  the 
wood,  and  the  ashes  are  all  the  rest,  so  testifies  our  bodily  eye.  The 
same  general  relation  Stahl  declared  to  be  true  for  the  metals;  they  con- 
sist of  the  calx  and  phlogiston.  But  the  mental  eye  of  Lavoisier^  saw 
the  calx  result  from  a union  of  the  metal  with  a spirit  invisible  to  the 
bodily  eye,  but  sensible  to  the  pointer  of  the  balance.  He  isolated  a 
portion  of  the  matter,  made  it  complete  an  entire  metamorphosis  by 
synthesis  and  analysis — and  the  vision  appearing  to  his  mind  had  become 
the  starting  point  for  the  work  of  a century. 


33.  NITROGEN,  PHOSPHORUS  # ARGON. 


1.  The  alchemists,  in  their  search  for  the  elixir,  subjected 
all  kinds  of  animal  materials  to  their  operations.  Brand,  at 
Hamburg,  in  1669,  while  doing  such  work,  produced  the  true 
phosphorus.  This  discovery  created  the  greatest  sensation  at 
the  time.  Having  concentrated  urine  by  freezing  or  by  evapo- 
ration, he  distilled  the  residue,  mixed  with  sand  and  charcoal 
dust,  gradually  increasing  the  temperature.  Now  phosphorus 
is  extracted  from  bones. 

2.  PHOSPHORUS  is  a soft,  colorless  (or  faintly  yellow) 
solid,  of  a specific  odor.  G 1.83,  F 44  degrees,  B 278.  It  is 
exceedingly  combustible  and  readily  inflammable;  it  must  be 
handled  with  great  care  and  is  kept  under  water.  Exposed  to 
the  air,  it  shows  a glow  of  light  in  the  dark,  whence  its  name 
(light-bearer).  It  burns  with  extreme  brilliancy  in  oxygen,- 
giving  solid,  white  phosphoric  oxide,  which  dissolves  in  water 
to  phosphoric  acid  (30,  10). 

3.  The  great  combustibility  of  phosphorus  permits  an 
approximate  analysis  of  atmospheric  air  to  be  made  as  lecture 
experiment.  In  a pneumatic  trough  is  placed  a tripod  support- 
ing a scorifier  on  which  is  placed  a coupel  with  a well  dried 
piece  of  phosphorus.  An  open,  well  dried,  bell  glass  is  set 
over  the  tripod,  and  resting  on  three  pieces  of  lead.  The 
water  should  be  at  least  three  inches  below  the  scorifier. 

4.  The  phosphorus  is  ignited  by  touching  it  with  the  heated 
end  of  a wire,  when  promptly  the  bell  glass  is  stoppered.  The 
burning  phosphorus  fills  the  glass  with  a cloud  of  white  oxide 
so  dense,  that  no  outline  of  the  objects  inside  can  be  dis- 
tinguished. The  surface  of  the  water  is  first  depressed  (due 
to  expansion)  but  soon  begins  to  rise,  marking  the  consump- 
tion of  the  oxygen. 

5.  The  combustion  ceases.  The  white  cloud  gradually  dis- 
appears, the  oxide  being  dissolved  in  the  water  to  phosphoric 


NITROGEN,  PHOSPHORUS  AND  ARGON. 


179 


acid — indicated  by  the  blue  litmus,  that  had  been  added  to  the 
water,  changing  to  red.  When  no  further  change  in  the  level 
of  the  water  takes  place,  the  water  inside  will  be  seen  to  occupy 
about  one -fifth  of  the  volume  originally  occupied  by  air. 

6.  To  examine  the  character  of  the  residual  air,  fill  the 
trough  suificiently  so  that  the  level  outside  again  stands  even 
with  the  level  inside  the  bell  glass.  Then  remove  the  stopper 
to  introduce  the  various  tests,  such  as  a burning  wax  taper, 
which  will  be  extinguished.  The  apparatus  being  promptly 
stoppered  after  each  test,  can  be  left  on  the  table  till  the 
next  day.  Then  filling  with  oxygen  equal  to  the  original 
volume,  and  after  equallizing  level  of  water,  the  air  will' 
soon  show  the  properties  of  atmospheric  air.  All  the  essential 
features  of  the  subject  will  be  recognized  in  this  form  of 
experiment,  which  is  perfectly  safe. 

7.  In  the  wet  way,  pyrogallic  acid  quite  promptly  absorbs 
oxygen  from  the  air,  if  an  excess  of  caustic  alkali  be  present; 
the  reagent  turns  deep  brown.  This  method,  due  to  Liebig 
(p.  23),  is  very  quick  and  sufficiently  exact.  It  can  be  used 
over  mercury  or  with  a gas  burette,  connected  with  an  absorp- 
tion gas  pipette. 

8.  A shower  of  electric  sparks,  passed  through  atmospheric 
air,  near  the  surface  of  water  (or  better,  a solution  of  caustic 
potassa)  soon  reduces  the  volume  considerably.  If  the  water 
was  tinted  with  cochineal,  it  will  show  acid  reaction.  From 
the  alkaline  solution  nitre  can  be  obtained.  Nitric  acid  has 
evidently  been  produced.  This  accounts  for  the  presence 
of  nitric  acid  in  rain  water  during  thunderstorms. 

9.  Cavendish,  who  first  made  this  synthesis  of  nitric  acid 
from  atmospheric  air  and  water,  added  pure  oxygen  whenever 
the  volume  diminished  no  longer.  But  he  found  it  impossible 
to  convert  the  entire  volume  of  air  into  acid ; about  one  per 
cent,  of  the  original  volume  remained. 

10.  These  remarkable  results  of  Cavendish  were  over- 
looked an  entire  century,  till  Lord  RALEIGH,  by  another 


180 


LECTURE  34. 


method,  obtained  the  same  non -absorbable  residual  volume  of 
nitrogen.  He  calls  this  gas  ARGON.  The  density  of  argon 
exceeds  that  of  nitrogen  50  per  cent. 

11.  When  absolutely  dry  nitrogen  gas,  entirely  free  from 
oxygen,  is  passed  over  magnesium  heated  to  barely  beginning 
redness  in  the  tube  of  a combustion  furnace,  the  nitrogen 
combines  with  the  metal.  The  magnesium  nitride  formed  is  a 
brownish  solid. 

This  property  of  magnesium  has  recently  become  very  use- 
ful for  the  extraction  of  argon  from  atmospheric  air. 

12.  When  magnesium  nitride  is  moistened,  the  odor  of 
ammonia  is  produced.  Mg  and  H Hate  give  H (am- 
monia) and  insoluble  Mg  Hate,  a mixture  of  hydrogen  and 
nitrogen  gas,  in  the  presence  of  an  acid,  exposed  to  a shower 
of  electric  sparks,  gives  the  ammonium  salt  of  that  acid. 
This  reaction  corresponds  exactly  to  that  of  Cavendish  (9). 


34.  BATTERY  AND  DYNAMO. 

1.  The  chemist  of  the  present  has  two  physical  powers  at 
his  service,  namely  HEAT  AND  ELECTRICITY.  The  chemist 
of  antiquity  only  possessed  the  first,  and  that  in  but  the  nar- 
row limits  from  the  freezing  of  water  to  a white  heat.  To-day, 
the  chemist  employs  temperatures  from  the  freezing  point  of 
oxygen  to  the  boiling  point  of  carbon,  and  uses  electricity  at 
his  pleasure. 

2.  The  application  of  electricity  in  the  chemical  arts  dates 
from  the  beginning  of  this  century,  when  VOLTA  (p.  31)  con- 
structed the  galvanic  BATTERY,  the  Voltaic  pile.  In  the  great 
chemical  industries,  electricity  could  not  be  used  until  the 
DYNAMO  had  cheapened  and  enlarged  its  flow  by  drawing  it 
from  a common  coal  fire  and  from  cataracts. 


BATTERY  AND  DYNAMO. 


181 


3.  The  voltaic  pile  consisted  of  pairs  of  plates  of  copper 
and  zinc,  separated  by  a moistened  rag  (1800).  Soon  the 
plates  were  enlarged  and  each  pair  placed  in  a distinct  vessel, 
containing  water;  such  single  CELLS  united  constitute  the 
BATTERY.  Water  being  replaced  by  salt  solution  or  by  dilute 
acid,  increased  the  power  greatly,  but  shortened  its  duration. 
Most  of  the  zinc  was  wasted,  being  consumed  without  pro- 
ducing electricity. 

4.  Zinc  in  dilute  acid  dissolves  with  evolution  of  hydrogen. 
Pour  a little  mercury  into  the  vessel,  and  the  evolution  stops, 
the  zinc  having  become  amalgamated,  or  coated  with  mercury 
on  its  surface,  and  mercury  is  insoluble  in  dilute  acid.  Pour 
some  of  the  acid  on  platinum  foil  in  another  tube — no  solution 
will  take  place,  no  effervescence  will  be  seen,  for  platinum 
requires  even  aqua  regia  for  its  solution. 

5.  But  pour  the  balance  of  the  first  glass  on  this  platinum, 
so  that  the  amalgamated  zinc  rests  upon,  or  at  least  touches 
the  platinum  foil ; instantly  the  evolution  of  hydrogen  will 
begin  again  and  be  more  abundant  than  with  the  zinc  alone. 
Furthermore,  the  hydrogen  does  no  longer  seem  to  rise  from 
the  zinc,  but  from  the  insoluble  platinum.  This  continues 
till  the  zinc  or  the  acid  is  consumed. 

6.  Both  the  amalgamated  zinc  and  the  platinum,  taken 
separately,  are  insoluble  in  the  dilute  acid.  Even  simply  lift- 
ing the  platinum  up  in  the  acid,  so  that  the  platinum  no  longer 
touches  the  amalgamated  zinc,  stops  the  evolution  of  gas  com- 
pletely. The  amalgamated  zinc  IN  CONTACT  with  the  plati- 
num is  soluble  in  dilute  acid,  when  not  in  such  contact  it  is 
insoluble. 

7.  Such  an  action  is  called  galvanic;  it  involves  the  pro- 
duction of  an  electrical  contrast  between  the  two  metals,  the 
amalgamated  zinc  and  the  platinum.  Accordingly,  in  a gal- 
vanic cell,  if  the  zinc  is  not  to  be  wasted,  but  only  to  be  used 
for  the  production  of  the  current,  the  zinc  must  be  thoroughly 


182 


LECTURE  34. 


amalgamated.  In  that  case  it  can  dissolve  only  while  the 
contact  is  produced  by  closing  the  circuit. 

8.  But  even  such  a cell  is  not  constant  yet.  The  other 
plate — copper — is  seen  to  become  coated.  Daniell  prevented 
this  by  placing  the  copper  in  a solution  of  blue  vitriol,  when 
pure  copper  deposited  while  the  current  is  used.  The  simplest 
construction  of  this  kind  we  have  in  the  GRAVITY  CELLS — 
copper  plate  in  heavy  blue  vitriol  solution  below,  the  zinc  plate 
in  lighter  dilute  acid  above. 

9.  The  most  effective  cells  yet  constructed,  are  those  of 
Grove  and  Bunsen  in  which  copper  is  replaced  by  platinum 
(Grove)  or  carbon  (Bunsen,  p.  24),  and  kept  pure  by  being 
inserted  in  concentrated  nitric  acid.  As  this  acid  would 
rapidly  dissolve  the  amalgamated  zinc,  the  nitric  acid  with  the 
Pt  or  C is  contained  in  a POROUS  CUP,  which  again  is  set  in 
the  dilute  acid  contained  in  the  glazed  cup  holding  the  zinc. 

10.  When  such  a cell  is  closed — that  is,  the  carbon  united 
with  the  zinc  by  a copper  wire  (conductor),  the  chemical 
action  sets  in,  and  an  electric,  or  rather  galvanic  current  flows 
through  the  wire — the  circuit.  Zinc  dissolves  as  zinc  sulphate 
in  the  outer  cup,  THE  HYDROGEN  PASSES  THROUGH  THE 
DILUTE  ACID  AND  THE  POROUS  CUP,  to  be  oxidized  to 
water  when  it  reaches  the  concentrated  nitric  acid.  This  is 
also  evidenced  by  the  rutilant  vapors  and  red  to  green  colora- 
tion of  the  acid.  The  acid  gradually  becomes  dilute,  but  the 
carbon  remains  free  from  gas.  THE  CELL  IS  CONSTANT. 

11.  That  a galvanic  CURRENT  passes  through  a closed 
circuit  is  readily  shown  by  the  production  of  heat  and  magnet- 
ism in  the  circuit.  The  first,  by  inserting  a thin  iron  or 
platinum  wire,  gradually  shortening  it,  till  it  glows  red  hot, 
white  hot  and  finally  melts.  The  second,  by  winding  the 
circuit  wire  around  soft  iron,  which  becomes  a temporary 
magnet  while  the  circuit  is  closed — an  electro-magnet. 

12.  With  such  electro-magnets,  powerful  machines  are 
constructed,  the  so-called  electric  MOTORS,  seen  on  our  street 


BATTERY  AND  DYNAMO. 


183 


railways  and  in  our  shops.  The  best  of  these  are  REVERSI- 
BLE, that  is,  if  moved  by  any  mechanical  power  (steam, 
hydraulic  turbine)  the  motor  produces  electricity;  it  is  then 
called  a DYNAMO.  These  furnish  the  electricity  required  in 
modern  chemical  works. 


Notes.  Four  Bunsen  cells  joined  in  series,  answer  for  all  necessary 
experiments.  The  hydrogen  current  going  in  each  cell  from  the  zinc 
through  the  liquid  to  the  other  solid  (C,  Pt,  Cu  in  the  different  kind  of 
cells)  the  galvanic  current  is  considered  to  flow  in  the  same  direction,  so 
that  the  exposed  carbon  (or  Pt,  Cu)  is  considered  the  positive  pole  of 
each  cell,  and  the  zixc  the  negative  pole.  Copper  wires  (best  insu- 
lated) attached,  carry  the  electrical  power  of  these  poles  as  good  conduc- 
tors; when  these  two  wires  are  brought  into  metallic  contact,  direct  or 
through  any  special  apparatus,  the  circuit  is  said  to  be  closed,  the  cur- 
rent will  pass  and  do  its  work. 

Attach  a file  to  one  of  these  wires,  and  draw  the  other  wire  along  the 
file;  a shower  of  sparks  of  burning  steel  will  be  seen,  especially  brilliant 
if  a thick  wire  coil  be  inserted.  The  production  of  heat,  magnetism  and 
motion  has  been  referred  to  in  the  text  proper. 

For  some  purposes,  the  current  is  intensified  by  induction.  A pri- 
mary COIL  of  heavy  wire  is  introduced  in  the  circuit,  which  is  automati- 
cally broken  and  closed  in  rapid  succession  by  an  iron  armature  attached 
to  a spring.  A very  long  and  very  thin  copper  wire,  thoroughly  insula- 
ted, forms  an  outer  secondary  coil  around  the  first  coil.  Connecting 
the  terminals  of  this  secondary  coil  with  tubes  containing  various  gases 
under  low  pressure,  they  will  be  illuminated  by  the  discharge  .(Geisler’s 
and  Plucker’s  Tubes).  Even  a shower  of  sparks  will  pass  through  air 
between  balls  or  wires  brought  into  proper  distance,  when  connected 
with  the  terminals.  Electricity  thus  produced  in  a near  conductor,  not 
in  metallic  contact  with  the  primary  conductor,  is  considered  produced 
by  induction.  Coils  of  this  kind  are  called  induction  coils.  The 
forms  devised  by  Ruhmkorff  are  the  best. 

The  great  subject  of  electric  induction  was  mainly  established  by  the 
researches  of  Faraday  (p.  26)  at  the  Royal  Institution  of  Great  Britain, 
from  1820  to  1850.  The  methods  found  application  on  a large  scale 
when  Siemens  and  Gramme  devised  practical  methods  of  winding  arma- 
tures. Great  electric  motors  and  dynamos  finally  were  constructed 
since  1870.  In  these  powerful  machines,  electric  engineering  applies 
the  electrical  science  qX  Oersted,  Ampere  and  Faraday,  and  permits  the 
economic  transmission  of  power  over  a single  wire  to  great  distances. 


35.  QUALITATIVE  ELECTROLYSIS. 


1.  Within  a month  after  Volta  had,  by  letter  to  the  presi- 
dent of  the  Royal  Society  of  London,  described  his  fertile 
invention,  two  English  chemists,  Nicholson  and  Carlisle,  suc- 
ceeded in  decomposing  water  by  the  current  of  the  voltaic 
pile.  This  was  the  first  step  into  ELECTRO-CHEMISTRY. 

2.  The  Hofmann  (p.  34)  DECOMPOSING  CELL  in  use  at 
lectures  consists  of  three  communicating  vertical  tubes.  The 
middle  one  has  a globular  reservoir  at  the  top.  The  two  late- 
ral tubes  are  provided  with  a glass  stop -cock  at  the  top  and 
with  platinum  ELECTRODES  near  the  lower  part.  These 
electrodes  consist  of  a rectangular  piece  of  platinum  foil,  sol- 
dered to  a platinum  wire,  which  is  fused  through  the  glass. 

3.  When  the  apparatus  is  filled  with  dilute  sulphuric  acid 
— pure  water  is  not  a conductor — and  the  electrodes  are  con- 
nected with  the  conducting  copper  wires  leading  to  the  poles  of 
the  battery,  bubbles  of  gas  form  immediately  and  rise  to  the 
top  in  a constant  stream.  The  volume  of  the  one  gas  is  seen 
to  be  twice  that  of  the  other. 

4.  Very  carefully  opening  the  stop-cock  over  the  larger 
volume,  the  issuing  gas  can  be  lit;  it  burns  with  a pale,  hot 
flame;  it  is  hydrogen.  The  other  gas  rekindles  a glowing 
shaving;  it  is  oxygen.  Careful  experiments  have  shown  that 
none  of  the  acid  disappears.  Accordingly,  the  galvanic  cur- 
rent has  decomposed  water  into  its  constituents,  oxygen  and 
hydrogen.  Their  ratio  of  volume  is  seen  to  be  one  to  two. 

5.  Tracing  the  connections  made  by  wire  between  the 
poles  of  the  battery  and  the  electrodes,  it  is  readily  seen  that 
the  current  of  hydrogen  in  the  decomposing  cell  flows  in  the 
same  direction  as  in  the  battery,  namely  from  the  zinc  through 
the  acid  to  the  other  solid  in  each  battery  cell.  This  is  also 
the  direction  assumed  by  physicists  for  the  current  of  positive 
electricity. 


QUALITATIVE  ELECTROLYSIS. 


185 


G.  Accordingly,  the  entire  circuit,  comprising  all  the  cells 
of  the  battery,  the  connecting  metallic  conductors  and  the  de- 
composing cell,  is  pervaded  by  one  continuous  electric  current 
flowing  in  the  same  direction.  Produced  in  the  battery  cells 
by  chemical  action,  directed  from  the  zinc  to  the  carbon,  it 
flows  in  the  same  direction  through  the  wire  to  the  decompos- 
ing cell,  accomplishes  its  chemical  work  and  continues  to  its 
origin.  Breaking  the  circuit  at  any  point,  the  entire  current 
stops  throughout. 

7.  Before  we  can  go  on  with  this  subject,  we  must  make 
ourselves  familiar  with  the  necessary  terms  in  use.  The 
last  carbon  of  the  battery  is  called  its  POSITIVE  POLE;  the 
wire  conductor  connecting  it  with  one  of  the  plates  of  the 
decomposing  cell  makes  this  plate  the  POSITIVE  ELECTRODE. 
The  other  pole  and  electrode  are  called  the  NEGATIVE.  Now, 
bodies  charged  with  unlike  electricities  attract  each  other,  but 
when  charged  with  like  electricities  they  repel  each  other. 
Supposing  the  hydrogen  drawn  to  the  negative  electrode,  or 
pushed  from  the  positive  electrode,  it  has  been  thought  to  be 
or  have  been  charged  with  positive  electricity.  At  any  rate, 
a substance  appearing,  like  hydrogen,  at  the  negative  electrode, 
is  CALLED  THE  ELECTRO-POSITIVE  CONSTITUENT  of  the 
substance  decomposed.  See  black-board  diagrams. 

8.  The  chemical  decomposition  effected  by  the  galvanic  cur- 
rent is  called  ELECTROLYSIS.  The  substance  decomposed 
is  called  the  ELECTROLYTE.  The  constituents  collecting  at 
the  electrodes  are  called  the  IONS.  Faraday  called  the 
electro  positive  ion,  collecting  at  the  negative  electrode  or 
CATHODE  the  cathion.  The  electro -negative  constituent 
appearing  at  the  positive  electrode  or  ANODE,  he  called  the 
anion. 

9.  For  more  careful  experiments  on  electrolysis  -attended 
with  the  evolution  of  gases,  it  is  advisable  to  use  simple  gas- 
collecting electrodes  of  the  following  form.  The  platinum 
wire  is  fused  into  a glass  tube  by  means  of  which  it  is 


186 


LECTURE  35. 


fastened  in  a good  cork  or  rubber  stopper.  This  stopper  also 
is  provided  with  a small  tube,  connected  with  rubber  to  carry 
the  gas  to  a gas  burette  or  the  pneumatic  trough.  The  stop- 
per is  inserted  in  a suitable  tube,  placed  into  the  electrolyte 
of  a stand  cylinder.  If  two  such  collectors  are  used,  both 
gases  can  be  collected  separately. 

10.  If  only  liquids  or  solids  are  to  be  collected,  a U-tube 
answers  as  decomposing  cell,  and  platinum  electrodes  can  be 
inserted  from  the  top. 

Using  a blue  vitriol  solution,  copper  deposits  as  the  negative 
electrode  (the  cathode).  Make  this  the  anode  (positive 
electrode)  and  the  copper  dissolves  again.  ■ Thus  copper — and 
other  metals — are  the  electro -positive  constituent  of  metallic 
salts,  and  metals  are  dissolved  at  the  positive  electrode. 

11.  The  solution  of  a neutral  salt,  like  potassium  sulphate, 
tinged  ruby-red  with  cochineal,  subjected  to  electrolysis  in  a 
U-tube  cell,  promptly  shows  a purple  tint  at  the  negative  and 
an  orange  tint  at  the  positive  electrode.  Consequently  the 
acid  is  the  electro -negative  constituent  of  neutral  salts,  while 
the  hydrate  is  the  electro -positive  constituent  thereof. 

12.  Accordingly,  SALTS  ARE  REALLY  DUAL  COM- 
POUNDS, as  first  concluded  from  the  solution  of  the  metals  in 
acids,  and  as  it  is  expressed  in  the  chemical  names  of  salts 
(for  example,  copper  sulphate). 

The  electro-positive  constituent  (cathion),  appearing  at  the 
negative  electrode  (cathode)  is  hydrogen,  metal  or  base. 

The  electro- negative  constituent  (anion),  appearing  at  the 
positive  electrode  (anode)  is  oxygen,  the  acid  radical  or  acid. 

By  secondary  (simple  chemical)  reaction,  the  radical  with 
water  gives  oxygen  set  free  and  the  acid.  Thus  Cu  S^te  gives 
a deposit  of  Cu  on  the  negative  electrode,  while  the  radical 
S^te,  appearing  at  the  positive  electrode,  must  decompose  the 
water,  uniting  with  H to  form  the  acid  H setting  free 

the  O gas.  . 


36.  APPLIED  ELECTROLYSIS. 


1.  The  synopsis  of  facts  presented  in  the  preceding  two 
lectures  barely  indicates  the  importance  of  the  galvanic  current 
to  chemistry.  In  this  lecture  a few  of  the  most  instructive 
special  scientific  and  technical  applications  of  electrolysis  will 
be  added  from  the  great  number  already  in  common  use,  and 
often  grouped  in  special  treatises  on  Electro-Chemistry. 

2.  Lavoisier  had  recognized  lime,  magnesia,  potassa  and 

soda  as  bodies  chemically 
resembling  metallic  calxes. 
Chemists  had  accordingly 
tried  to  produce  such  metals 
from  them.  Subjecting  solid 
caustic  potassa  to  electroly- 
sis, HUMPHRY  DAVY,  at 
the  Royal  Institution,  no- 
ticed the  separation  of  min- 
ute white,  metallic  globules, 
burning  almost  as  soon  as 
formed.  Thus  the  light 
metals  (Ka,  Na,  Mg,  Ca, 
Sr,  Ba,  etc.,)  were  first 
produced  in  1807. 

3.  The  finely  pulverized  mineral  fluorite  (11,  10)  treated 
with  rather  concentrated  sulphuric  acid  in  a covered  dish  of 
lead  gives  a most  poisonous  gas,  which  is  an  acid  and  has  the 
special  property  of  dissolving  silica.  It  is  used  to  etch  glass 
where  not  protected  by  a film  of  wax.  The  supposed  non- 
metallic  or  electro- negative  constituent  of  this  acid  was  called 
FLOURINE  after  the  mineral,  which  itself,  was  called  calcium 
fluoride,  .while  the  acid  was  called  hydrogen  fluoride. 

4.  All  attempts  to  produce  this  hypothetic  substance  fluor- 
ine failed  until  1886,  when  MOISSAN  (p.  36)  at  the  School  of 
Pharmacy  of  Paris,  succeeded  in  isolating  and  confining  this 


HUMPHRY  DAVY. 


188 


LECTURE  36. 


the  most  active  of  all  substances.  He  obtained  it  by  the  elec- 
trolysis of  the  absolute  (anhydrous)  acid,  in  which  anhydrous 
potassium  fluoride  had  been  dissolved  to  make  the  liquid  a 
conductor.  The  decomposing  cell  had  to  be  made  of  platinum, 
closed  by  stoppers  of  transparent  fluorspar.  The  liquid  was 
cooled  to  50  below  freezing. 

5.  FLUORINE  appeared  as  a greenish  yellow  gas;  liquefy- 
ing at  95  degs.  below  freezing.  It  combines  with  mercury  at 
common  temperatures,  and  with  iron  or  even  platinum  at  a 
moderate  heat.  Iodine,  sulphur,  phosphorus,  arsenic  and  car- 
bon burst  into  flame  in  fluorine.  Hydrogen  and  fluorine  unite 
even  in  the.dark  with  explosion.  Fluorine  decomposes  water 
instantly,  giving  ozone  and  hydrofluoric  acid.  Hence  the 
necessity  of  removing  all  traces  of  water  to  isolate  fluorine. 

6.  Fluorine  is  the  most  strongly  electro- negative  substance 
known,  precisely  as  potassium  is  the  most  electro-positive. 
Both  have  been  first  produced  by  electrolysis.  Both  decom- 
pose water  at  common  temperatures.  The  metal  potassium 
takes  the  place  of  the  hydrogen,  while  the  non-metal  fluorine 
takes  the  place  of  the  oxygen,  by  substitution. 

7.  While  the  isolation  of  fluorine  cannot  be  exhibited  to  a 
class,  it  is  very  irrstructive  to  prepare  and  exhibit  the  corres- 
ponding non -metallic  constituent  of  muriatic  acid.  The  two 
cases  are  every  way  parallel.  The  liquid  used  is  a saturated 
solution  of  salt  with  one -tenth  its  volume  of  concentrated 
muriatic  acid.  Electrodes  of  carbon  have  to  be  used,  this  gas 
readily  attacking  platinum  at  common  temperatures. 

8.  The  poisonous  gas  must  be  confined  in  a series  of 
absorption  flasks,  Drechslers  and  columns.  To  avoid  any  gas 
escaping  into  the  air,  the  last  column  should  be  charged  with 
pumice  wet  with  a strong  solution  of  caustic  potash.  In  a dish, 
aqua  ammonia  should  be  handy  to  remove  the  gas  that  may 
escape  when  substances  are  introduced  into  the  glass  vessels. 

9.  The  gas  produced  at  the  positive  electrode  is  yellowish 
green — hence  it  has  been  called  CHLORINE  by  Davy,  1810. 


APPLIED  ELECTROLYSIS. 


189 


It  bleaches  and  destroys  organic  colors;  it  explodes  with 
hydrogen;  pulverized  metallic  antimony  thrown  into  a cylinder 
with  chlorine  burns  brightly.  Potassium  bursts  into  flame  in 
chlorine.  Its  tendency  to  combine  with  hydrogen  makes  it 
destructive  to  organic  tissue. 

Chlorine  is  largely  absorbed  by  water,  forming  chlorine 
water.  This  possesses  the  bleaching  effects  of  the  gas,  and 
dissolves  even  gold  and  platinum  in  the  cold  to  chlorides 
(19,  5). 

10.  Scheele  first  produced  this  gas  (1774)  by  warming 
pyrolusite  (9.7)  with  muriatic  acid;  he  called  it  PHLOGISTI- 
CATED  MURIATIC  ACID.  When  oxygen  had  been  recognized, 
Berthollet  called  it  OXYGENATED  MURIATIC  ACID  (1785). 
Lavoisier  had  supposed  oxygen  to  be  essential  to  all  acids,  as 
implied  by  the  name:  acid  producer.  Davy  proved  (1808) 
that  muriatic  acid  contains  no  oxygen,  but  consists  of  the  two 
substances  hydrogen  and  CHLORINE  only.  Consequently 
MURIATES  ARE  CHLORIDES;  and  the  equivalent  of  chlorine 
therefore  is  35.5.  See  27,  10. 

11.  By  the  method  of  Scheele,  chlorine  gas  is  produced  on 
a large  scale.  Absorbed  by  lime  and  dilute  cold  alkalies,  the 
so-called  HYPOCHLORITES  result  (Ca,  bleaching  powder ; Ka, 
eau  de  Javelle;  Na,  Labarraque’s  liquid).  These  are  effective 
bleaching  and  disinfecting  compounds.  A warm  concentrated 
solution  of  caustic  potassa  yields  crystals  of  POTASSIUM 
CHLORATE  (30,  8).  The  residue  left  after  heating  this 
salt  to  obtain  oxygen,  crystallizes  in  cubes  from  its  solution; 
it  is  POTASSIUM  CHLORIDE. — These  compounds  can  all  be 
obtained  by  the  electrolysis  of  potassium  chloride. 

12.  Electrolysis  has  long  been  applied  in  the  arts  for  elec- 
troplating (gold,  silver),  electrotyping  (Cu)  and  even  in  the 
metallurgy  of  copper  and  gold.  Since  the  dynamo  furnishes  a 
cheap  and  powerful  electrical  current,  chemical  manufacturing 
is  changing  to  a considerable  extent,  by  the  substitution  of 
electrolytical  for  purely  chemical  processes.  We  shall  come 
back  to  this  subject  later  on. 


37.  EQUIVALENT  AND  ELECTRICITY. 


1.  In  electrolysis  we  have  a decomposition  of  a compound 
into  its  constituents  without  the  addition  of  special  reagents, 
excepting  the  presence  of  a volatile  acid  or  the  results  of 
secondary  reactions.  Accordingly,  electrolysis  may  be  ex- 
pected to  furnish  QUANTITATIVE  METHODS  OF  HIGH  PRE- 
CISION for  the  determination  of  many  substances.  Experience 
has  fully  confirmed  this  expectation. 

2.  Not  only  the  most  accurate,  but  at  the  same  time  the 
most  RAPID  DETERMINATION  of  nearly  all  metals,  is  effected 
by  electrolysis.  The  substance  is  weighed  in  a PLATINUM 
DISH  and  dissolved  therein.  The  dish  is  made  the  negative 
electrode,  and  the  current  kept  up  till  no  longer  a trace  of  the 
metal  can  be  detected  in  a drop  of  the  solution.  Then  the 
solution  is  poured  off,  the  metal  generally  adhering  to  the  dish, 
is  washed  with  water,  then  with  alcohol ; finally  it  is  dried 
and  weighed,  still  on  the  dish. 

3.  NO  TRANSFERS  having  been  made,  a number  of  serious 
errors  affecting  all  other  analytical  processes,  are  avoided  in 
electrolysis.  The  solutions  most  serviceable  are  nitrates, 
sulphates  and  cyanides,  exemplified  in  silver,  copper  and  gold 
determinations.  The  degree  of  temperature,  and  the  density 
of  the  current  (amount  per  square  centimeter  of  negative 
electrode)  are  of  influence  on  the  results. 

4.  Even  if  more  than  one  metal  be  present,  electrolytic 
determinations  of  each,  in  the  same  sample,  are  generally 
possible ; for  the  tension  required  for  the  separation  of  metals 
in  electrolysis  varies  considerably,  and  the  acid  or  solvent 
used  is  of  great  influence.  Thus  copper  is  deposited  by  much 
less  electrical  tension  than  nickel.  The  investigations  of 
Professor  Edgar  F.  Smith,  of  Philadelphia,  have  been  success- 
fully centered  on  this  practically  important  field ; his  special 
methods  are  advantageously  followed  in  the  laboratories. 

5.  STRIKING  EFFECTS  OF  GALVANIC  ACTION,  have, 
however,  long  been  used  IN  QUALITATIVE  ANALYSIS.  Thus, 


EQUIVALENT  AND  ELECTRICITY. 


191 


metallic  zinc  reduces  all  the  metals  of  the  arsenic  group;  anti- 
mony and  tin  separate  often  in  crystal  form,  arsenic  largely 
escapes  as  gaseous  hydrides,  if  sulphuric  acid  is  used.  The 
solutions  are  supposed  to  be  contained  in  a watch  glass,  to 
permit  examination  by  magnifier  or  microscope. 

But  if  instead  of  a watch  glass,  the  cover  of  a platinum 
crucible  be  used  to  contain  the  acidfied  liquid,  galvanic  action 
sets  in.  The  current  in  the  cell  will  go  from  the  zinc  through 
the  acid  to  the  platinum;  hence  the  bubbles  of  hydrogen  gas 
will  appear  at  the  platinum  only.  If  antimony,  even  a bare 
trace,  be  present,  it  will  go  with  the  current,  STAINING  THE 
PLATINUM  BLACK  (or  brown  if  exceedingly  little  be  present). 
Neither  tin  nor  arsenic  stains  the  platinum.  The  tin  deposits 
on  the  zinc.  The  arsenic  largely  escapes,  as  stated. 

6.  By  connecting  a pair  of  gas-collecting  electrodes  (35,  9) 
each  with  a gas  burette,  while*  the  electrodes  are  placed  in 
water,  acidified  with  sulphuric  acid,  the  hydrogen  and  oxygen 
gas  can  be  most  accurately  measured.  The  volume  of  the 
hydrogen  will,  at  every  instant,  be  twice  that  of  the  oxygen. 
But  direct  weighings  have  shown  oxygen  to  weigh  16  times  as 
much  as  an  equal  volume  of  hydrogen  (3,  12).  Hence  the 
weights  obtained  are  as  16  to  2 or  8 to  1.  Electrolysis  gives 
the  equivalent  of  oxygen  8,  as  found  before  by  direct  chemical 
means  (31,  3-5). 

7.  If  a strong  current  is  used,  the  volume  of  oxygen  gas 
possesses  a marked  odor  and  is  less  than  half  that  of  hydrogen. 
It  has  been  found,  that  a portion  of  the  oxygen  has  been  con- 
densed, its  density  being  increased  50  per  cent.  This  con- 
densed oxygen  is  called  OZONE.  It  is  very  much  more  active 
than  ordinary  oxygen.  It  decomposes  potassium  iodide,  which 
oxygen  does  not  do. 

For  these  reasons  it  is  best  to  measure  the  hydrogen  only 
for  quantitative  purposes. 

8.  Since  the  hydrogen  passes  over  continuously,  its  volume 
at  any  given  time  is  a measure  of  the  total  electrical  current 
used  up  to  that  time.  Instruments  for  the  measurement  of 


192 


LECTURE  37. 


the  galvanic  current  by  the  chemical  effect  produced  are  called 
VOLTAMETERS.  The  unit  used  is  called  the  Ampere;  it 
corresponds  to  6 mgr.  hydrogen  in  ten  minutes  time,  or  to  7.2 
cc  hydrogen  gas  per  minute  at  common  temperatures  and 
pressure  (i.  e.  when  one  mgr-Mg  yields  one  cc  hydro- 
gen gas).  . 

9.  If  a number  of  decomposing  cells  of  the  same  kind,  say 
charged  with  the  same  acidified  water,  be  inserted  in  series  in 
the  same  circuit,  the  electrolysis  in  all  will  not  only  be  the 
same  in  kind  or  quality,  but  also  the  same  in  amount  quanti- 
tatively. This  equality  remains,  independent  of  any  difference 
in  form,  magnitude  or  character  of  the  different  decomposing 
cells,  placed  in  the  same  circuit.  This  proves,  that  THE  IN- 
TENSITY OF  A GALVANIC  CURRENT  IS  THE  SAME  AT  ALL 
POINTS  OF  THE  CIRCUIT.  This  fact  is  really  assumed  in 
the  use  of  the  voltameter. 

10.  If  the  different  cells,  inserted  in  series  in  the  same 
circuit,  contain  different  compounds,  the  ELECTROLYSIS 
SEPARATES  CHEMICALLY  EQUIVALENT  AMOUNTS  IN  THE 
DIFFERENT  CELLS  in  the  same  time.  Thus,  acidified  water, 
a copper  solution,  and  a silver  solution,  connected  in  continu- 
ous series,  yield  qualitatively,  at  the  negative  electrodes, 
the  positive  constituents:  hydrogen,  copper  and  silver.  Re- 
ducing the  volume  of  hydrogen  to  weight,  the  proportions 
are  invariably  as  1 : 31.75  : 108,  that  is,  as  the  equiva- 
lents of  H,  Cu,  Ag.  This  is  the  electrolytic  law  of  Faraday 
(p.  26). 

11.  A mercurous  and  a mercuric  solution,  placed  in  the 
same  circuit,  yield  double  the  weight  of  mercury  in  the  first. 
The  equivalent  of  mercury  in  mercuric  compounds  has  been 
found  to  be  100;  in  mercurous  it  is  therefore  200.  In  a like 
manner,  the  equivalent  of  iron,  in  ferrous  solutions,  is  known 
to  be  28  (18,  10) ; but  in  feric  solutions,  it  is  only  two-thirds 
thereof,  or  18.66.  The  symbol  for  the  — ous  compounds  has 
frequently  been  distinguished  by  small  initial,  thus  hg  200, 
fe  18.66. 


EQUIVALENT  AND  ELECTRICITY. 


193 


12.  In  this  manner,  the  ELECTROLYTIC  EQUIVALENT  of 
many  substances  has  already  been  determined  by  Faraday 
(1834) ; the  value  found  was  always  the  same  as  the  CHEMI- 
CAL EQUIVALENT  determined  by  chemists  without  use  of 
electricity.  Consequently,  electrolysis  takes  place  according 
to  the  proportions  of  the  chemical  equivalents.  This  is  the 
LAW  OF  FARADAY.  Fusible  substances  were  also  decom- 
posed in  the  dry  way,  keeping  them  liquid  by  fusion.  This 
avoids  all  secondary  reactions  caused  by  the  presence  of 
water  (35,  12). 


38.  EQUIVALENT  AND  VOLUME. 

1.  Electrolysis  shows  that  water  contains  two  volumes  of 
hydrogen  gas  for  every  one  volume  of  oxygen  gas  (35,  3,  4). 
Evidently  we  may  consider  the  two  volumes  of  hydrogen  gas 
chemically  equivalent  to  one  VOLUME  of  oxygen  gas,  precise- 
ly as  we  have  called  the  corresponding  WEIGHT  one  of  hydro- 
gen, chemically  equivalent  to  the  weight  eight  of  oxygen. 

2.  But  in  doing  so  we  would  use  the  same  term  equivalent 
for  relations  of  WEIGHT  and  of  MEASURE  (or  volume).  This 
slight  imperfection  of  expression  has  been  avoided,  by  speak- 
ing of  volumes  as  HAVING  A VALENCE  (worth),  while 
weights  continue  to  be  spoken  of  as  BEING  EQUIVALENT. 
Thus  chemists  say:  8 mgr.  oxygen  are  equivalent  to  1 mgr. 
hydrogen;  and  also:  one  volume  of  oxygen  gas  has  the 
valence  of  two  volumes  of  hydrogen  gas. 

3.  If  we  adopt,  for  gases,  the  measure  or  volume  as  unit, 
and  represent  ONE  volume  by  ONE  symbol  in  roman  type, 
(to  distinguish  it  from  the  equivalent  weights  printed  in 
italics),  then  the  VOLUME  FORMULA  of  water  evidently 
becomes  H2O. 

The  equivalent  formula  HO  is  no  less  true,  for  it  refers  to 
equivalent  WEIGHTS.  Both  formulae  express  FACTS  well 


194 


LECTURE  38. 


determined;  in  one  case,  they  relate  to  weight,  in  the  other, 
to  gas  measure  (volume). 

4.  In  the  electrolysis  of  MURIATIC  ACID,  the  gases  pro- 
duced can  also  readily  be  measured  by  our  gas  burette;  we 
need  only  interpose  our  air  lock,  or  any  dry  cylinder  contain- 
ing atmospheric  air,  between  the  decomposing  cell  and  the 
burette.  The  chlorine  will  push  the  air  into  the  burette,  but 
not  itself  come  in  contact  with  the  water. — The  experiment 
shows  the  volume  of  the  chlorine  to  be  equal  to  that  of  the 
hydrogen.  Chlorine  therefore  has  the  valence  one.  The 
volume  formula  of  hydrogen  chloride  is  H C 1,  the  same  as  its 
equivalent  formula,  H C I, — After  each  experiment,  the  air 
lock  must  be  properly  ventilated. 

5.  AQUA  AMMONIA  can  also  be  electrolysed.  Most  suitable 
is  a concentrated  solution  of  salt,  to  which  not  more  than 
one -tenth  its  own  volume  of  the  strongest  aqua  ammonia  has 
been  added.  Hydrogen  will  appear  at  the  negative  electrode, 
nitrogen  at  the  positive  electrode.  The  volume  of  hydrogen  is 
exactly  three  times  that  of  the  nitrogen.  That  is,  the  valence 
of  nitrogen  is  three,  or  one  volume  of  nitrogen  is  equivalent  to 
three  volumes  of  hydrogen.  The  volume  formula  of  ammonia 
is  therefore  H3N.  Its  equivalent  formula  is  HN, 

6.  The  equivalent  of  nitrogen,  by  weight,  has  been  found 
to  be  4|.  That  is,  the  weight  of  three  volumes  of  hydrogen 
is  to  that  of  one  volume  of  nitrogen  as  1 to  4|.  Consequently, 
the  weight  of  one  volume  of  hydrogen  is  to  that  of  one  volume 
of  nitrogen,  as  ^ to  4|,  or  as  1 to  14.  If  the  weight  of  one 
volume  of  hydrogen  be  taken  as  unit,  one  volume  of  nitrogen 
should  weigh  14  such  units.  Actual  experiments  have  shown 
such  to  be  the  case  (3,  12). 

7.  It  is  true,  all  determinations  made  prior  to  1895,  gave 
14.04;  but  as  Lord  Rayleigh  has  shown,  this  was  due  to  the 
fact,  that  the  presence  of  the  heavier  argon  in  the  nitrogen 
had  been  overlooked  (33.10).  When  making  weighings  with 
pure  nitrogen,  free  from  argon.  Lord  Rayleigh  no  longer  found 


EQUIVALENT  AND  VOLUME. 


195 


14.04,  but  14.00  as  the  weight  of  one  volume  of  nitrogen. 
This,  accordingly,  is  the  volume  weight  of  nitrogen. 

8.  In  the  same  way,  the  volume  weight  of  oxygen  must  be 
16.  For  the  two  volumes  of  hydrogen  gas,  equivalent  to  one 
volume  of  oxygen,  prove  oxygen  to  be  divalent.  The  equiva- 
lent weights  1 to  8 are  as  2 to  16 ; hence  one  volume  of  oxygen 
gas  should  weigh  16,  one  of  hydrogen  gas  weighing  1. 
Actual  weighings  have  confirmed  this  conclusion. 

9.  For  practical  purposes  the  UNIT  OF  GAS  VOLUME  is 
that  containing  one  milligramme  of  hydrogen;  under  common 
conditions  of  temperature  and  pressure,  12  cc.  To  determine 
this  unit  under  any  given  conditions  of  pressure  and  tempera- 
ture, find  the  volume  occupied  by  the  hydrogen  gas  generated 
from  12  mgr.  pure  magnesium.  See  18,  9. 

10.  The  valence  of  carbon  cannot  be  determined  directly, 
because  carbon  is  not  known  as  a gas.  But  fixed  air  contains 
8 oxygen  to  3 carbon  (31,  7) ; or  two  equivalents  of  oxygen  to 
one  equivalent  of  carbon  weighing  6 (31,  8).  But  direct  ex- 
periments show,  that  when  carbon  is  burnt  in  oxygen,  the  gas 
volume  does  not  change.  Since  now  one  volume  of  oxygen  is 
equivalent  to  two  volumes  of  hydrogen,  carbon  must  have  the 
valence  4.  All  the  numerous  compounds  of  carbon  confirm 
this  conclusion. 

11.  THE  VALENCE  of  a gas  is  the  number  of  volumes  of 
hydrogen  chemically  equivalent  to  one  volume  of  the  gas. 
By  electrolysis  we  have  found  chlorine  to  be  monovalent, 
oxygen  divalent  and  nitrogen  trivalent;  that  is,  these  gases 
have  respectively  the  valence  1,  2,  3.  By  reasoning  and  cal- 
culation, carbon  is  tetravalent.  All  of  organic  chemistry  will 
confirm  this  conclusion. 

12.  If  three  decomposing  cells,  charged  with  muriatic 
acid,  water,  and  ammonia,  are  inserted  in  series  in  the  circuit 
of  a battery— say  of  eight  Bunsens — the  hydrogen  gas,  at  the 
negative  electrodes,  will  always  be  of  exactly  the  same  volume 


198 


LECTURE  38. 


in  all  three  decomposing  cells,  in  accordance  with  the  general 
law  of  Faraday  (36,  9,  10).  At  the  positive  electrode,  the 
volume  of  chlorine  will  be  equal  to  that  of  the  hydrogen ; the 
volume  of  oxygen  will  be  half,  that  of  nitrogen  one  third  the 
volume  of  hydrogen.  This  form  of  experiment,  due  to  Hof- 
mann (p.  34)  strikingly  shows  that  Cl,  O and  N have  the 
valence  1,  2,  3. 


Notes  8.  Such  gas  weighings,  for  the  purpose  of  verifying  the  data 
given,  are  readily  made,  without  the  use  of  air  pump,  by  taking  the 
hydrogen  filled  tube  as  standard  of  comparison. 

I use  a LT-tube  with  side  tubes  and  perforated  ground  glass  stopper,  of 
capacity  50  to  100  cc,  and  with  fine  wire  for  suspension  to  balance;  weigh 
to  tenth  milligramme.  For  each  gas  to  be  weighed,  a Kipp  generator  is 
used,  but  only  one  set  of  absorption  and  drying  tubes,  as  slow  but  com- 
plete displacement  is  required  anyway. 

First,  fill  tube  with  pure,  dry  hydrogen  and  weigh;  say  the  weight  is  a. 
Then  connect  with  oxygen-Kipp,  and  weigh  again;  say  it  is  b.  Also 
fill  with  fixed  air;  let  weight  be  c.  Evidently  b-a  is  the  weight  of  oxygen 
over  hydrogen,  proportional  to  16-1  = 15;  and  in  the  same  way  c-a  is 
proportional  to  22-1=21.  That  is,  the  experiment  must  show  the  differ- 
ence c-a,  divided  by  the  difference  b-a  to  be  equal  to  21  divided  by  15, 
which  is  1,40.  Actual  experiment  will  show  this  to  be  the  case,  very 
nearly,  and  thus  verify  the  statement,  made  in  the  lecture.  It  is  evident 
that  c-a  divided  by  21  should  be  very  nearly  equal  to  b-a  divided  by  15; 
for  both  quotients  represent  the  weight  of  the  dry  hydrogen  gas  filling 
the  weighing  tube  This  checks  the  accuracy  of  the  work  done. 

Finally,  if  at  the  same  time  a determination  of  the  unit  volume, 
(approximately  12  cc)  has  been  made,  while  the  weighings  were  going  on 
(see  section  9),  and  if  the  capacity  in  cc  of  the  weighing  tube  has  been 
ascertained  beforehand  by  weighing  it  with  air  and  with  water,  the 
weight  of  the  unit  volume  of  hydrogen  gas  will  be  determined  by  divid- 
ing that  unit  volume  into  the  volume  of  the  weighing  tube,  giving  the 
NUMBER  of  unit  volumes  handled;  dividing  this  number  into  the  weight 
of  hydrogen  filling  the  tube,  as  just  determined,  will  give  the  weight  of  a 
unit  volume  of  hydrogen  gas.  This  should  be  equal  to  one. 

Since  hydrogen  gas  escapes  readily,  even  during  a weighing,  and  as  all 
other  gases  replacing  it  are  heavier,  the  weight  is  likely  to  be  found  a 
trifle  above  one.  Morley’s  results. 


39.  EQUIVALENT  AND  HEAT. 


1.  The  determination  of  the  volume  of  substances  by  the 
method  just  described,  is  palpably  restricted  to  gaseous 
bodies;  to  the  much  larger  class  of  metals  it  is  inapplicable. 
As  has  first  been  shown  in  1819,  by  DULONG  and  PETIT,  a 
determination  of  the  specific  heat  of  metals  will  establish 
this  volume. 

2.  All  amounts  of  heat  are  measured  in  gramme -degrees 
(25.11).  The  instrument  used  for  such  measurement  is 
called  a CALORIMETER.  It  consists  of  a metallic  vessel, 
provided  with  stirrer  and  a sensitive  thermometer;  it  is  placed 
in  another  metallic  vessel  to  minimize  the  loss  of  heat  to  the 
surroundings.  Details  of  construction  belong  to  laboratory 
practice. 

3.  Usually  water  is  used  as  the  HEAT  MEASURING  LIQUID. 
Suppose  100  cc  water  were  used  in  the  calorimeter;  and  suppose 
the  temperature  reads  20  degrees.  If  now  10  cc  boiling  water 
(of  100  degrees)  be  added,  the  temperature  will  rise  to  27.3 
degrees. 

The  100  cc  originally  in  the  calorimeter  rose  7.3  degrees, 
amounting  to  730  gramme-degrees.  The  10  cc  were  cooled 
from  100  to  27.3  degrees,  or  72.7  degrees,  giving  off  727  gro 
or  practically  as  much  as  the  100  cc  gained. 

4.  If,  under  the  same  circumstances,  100  grammes  of  sheet 
COPPER,  in  the  form  of  bent  cuttings,  be  rapidly  transferred 
from  a beaker  with  boiling  water  to  the  calorimeter  charged 
with  100  cc  water  of  20  degrees,  the  temperature  will  also  rise 
to  very  nearly  27.3  degrees.  Hence,  100  gr.  copper  yield 
as  much  heat  as  10  degrees  water  in  the  preceding  experi- 
ment; or  one  gramme  of  copper  carries  no  more  heat  per 
degree,  than  one-tenth  of  a gramme  of  water. 

5.  The  amount  of  heat  required  to  change  the  temperature 
of  one  gramme  of  any  substance  one  degree  (centigrade)  is 
called  the  SPECIFIC  HEAT  of  that  substance.  For  copper  it 


198 


LECTURE  39. 


has  just  been  found  to  be  0.1,  very  nearly.  Careful  experi- 
ments, allowing  for  all  influences,  make  it  0.094. 

6.  If  we  multiply  the  specific  heat  by  the  equivalent,  we 
obtain  the  EQUIVALENT  HEAT,  that  is,  the  amount  of  heat 
(in  gro)  required  to  change  the  temperature  of  one  gramme - 
equivalent  one  degree.  The  following  table  gives  the  deter- 
minations of  specific  heat,  mainly  by  REGNAULT  (1840). 


7.  TABLE  of  specific  heat,  equivalent  weight  (Eq.)  and 
equivalent  heat  (Eq.  H)  of  the  principal  metals. 


Metal. 

Sp. 

Eq. 

Eq.  H. 

Metal. 

Sp. 

Eq. 

Eq.  H. 

Na.  . . . 

0.293 

23 

6.74 

Cu.  . . . 

0.094 

31.8 

2.98 

Mg.  . . . 

0.250 

12 

3.00 

Ag.  . . . 

0.057 

108 

6.16 

Al.  ... 

0.214 

9 

1-93 

Cd.  . . . 

0.057 

66 

3-76 

Ka.  . . . 

0.166 

39 

6.47 

Hg.  . . . 

0.033 

100 

3-30 

Fe.  ... 

0.II4 

28 

3-19 

Au.  . . . 

0.032 

66 

2.1 1 

Zn.  ... 

0.096 

32.5 

3-13 

Pb.  ... 

0.031 

104 

3.22 

8.  Of  these  metals,  sodium  and  potassium  were,  already 
by  Berzelius,  considered  to  be  equivalent  to  hydrogen,  or  in 
our  modern  language,  to  be  monovalent.  Their  equivalent 
heat  is  about  6.5.  Silver  comes  the  nearest.  The  mean  of 
these  three  is  6.44.  This,  therefore,  is  the  equivalent  heat 
of  metals  having  the  VALENCE  ONE. 

9.  The  seven  metals:  Mg,  Fe,  Zn,  Cu,  Cd,  Hg  and  Pb 
show  equivalent  heat  a little  above  3.  The  mean  of  all  is 
3.23.  This  is  evidently  half  the  value  of  the  preceding 
group.  Doubling  3.23  give  6.46,  practically  identical  with 
the  equivalent  heat  of  the  monovalent  metals.  Two  equiv- 
alents must  be  taken  to  get  the  same  heat  capacity,  6.5. 

10.  The  equivalent  heat  of  A1  and  Au  averages  2.02,  very 
nearly  one-third  of  that  of  the  first  group.  The  specific  heat 
of  three  equivalents  of  these  metals  is  6.06.  Gold  and  alum- 
inium must,  therefore,  so  far  as  heat  is  concerned,  be  taken  in 
three  equivalents. 

11.  The  specific  heat  of  carbon  varies  greatly  with  tem- 
perature and  condition.  For  charcoal  it  is  0.241,  for  graphite 
0.197  and  for  the  diamond  0.147.  No  conclusion  as  to  val- 


EQUIVALENT  AND  HEAT. 


199 


ence  should  be  drawn  from  these  data,  which  simply  illustrate 
the  allotropic  conditions  of  carbon.  The  specific  heat  of 
carbon  rapidly  increases  with  the  temperature.  At  some  tem- 
perature it  is  concordant  with  the  other  substances.  See  42 
and  compare  38.10.  The  specific  heat  of  S,  0.177  and  lo,  0.054. 
with  the  equivalents  16  and  127  give  2.83  and  6.86.  Hence, 
S is  divalent,  lo  monovalent. 

12.  For  the  gases  H,  N,  O,  the  specific  heat  has  been 
found  3.41,  0,244  and  0.218.  The  equivalents  being  1,  4|  and 
8,  the  equivalent  heats  are  3.41,  1.14  and  1.74.  This  agrees 
with  the  valence  as  determined  by  electrolysis.  1,  3,  2,  yield- 
ing 3.41,  3.42  and  3.48  respectively  for  1,  3,  and  2 volumes. 

Thus  the  valence  of  metals  and  non-metals  is  concordantly 
determined  by  volume  and  by  specific  heat. 


40.  ATOMS  AND  MOLECULES.. 

1.  The  solution  of  metals  showed  that  certain  definite 
WEIGHTS  of  the  different  metals  are  chemically  equivalent. 
One  hydrogen  was  found  equivalent  to  12  magnesium,  28  iron 
and  100  mercury.  In  electrolysis  it  was  found  that  equal 
quantities  of  electricity  set  free  the  same  equivalent  weights 
of  metals. 

2.  But  these  equivalent  weights  are  not  of  the  same  value 
in  reference  to  heating  and  space-occupying  capacity;  still, 
they  differed  in  simple  ratios,  requiring  one,  two,  three  or 
four  equivalents  to  obtain  the  same  heat  capacity,  or  having 
the  space-occupying  capacity  of  1,  2,  3,  4 equivalents  of 
hydrogen  gas. — Here  we  have  exclusively  FIXED,  SIMPLE 
MULTIPLE  PROPORTIONS. 

3.  Neither  equivalent  alone,  nor  valence  alone,  fully  char- 
acterizes any  given  kind  of  matter,  such  as  H,  O,  N,  C or  Ka, 
Mg,  Al;  Si;  both  are  required  and  expressed  in  the  higher 
chemical  unit,  the  ATOM. 

AN  ATOM  IS  A RELATIVELY  INDIVISIBLE  PARTICLE  OF 
MATTER.  It  possesses  a definite  number  of  valencies,  acting 


200 


LECTURE  40. 


like  single  EQUIVALENTS.  That  is,  the  atomic  weight  is 
equal  to  the  product  of  its  valence  into  its  equivalent  weight. 

4.  Hydrogen  is  the  chemical  unit,  being  the  smallest.  Its 
equivalent  is  one,  its  valence  is  one;  hence  also  its  atomic 
weight  is  one. 

Oxygen  has  a valence  two,  and  its  equivalent  is  8;  there- 
fore its  atomic  weight  is  16.  Nitrogen  has  a valence  3,  its 
equivalent  is  4S;  hence  its  atomic  weight  is  14.  Carbon  has 
the  valence  4,  the  true  equivalent  3,  the  atomic  weight  12. 

5.  The  product  of  equivalent  into  specific  heat  for  Ka,  Na, 
Ag  was  6.4  (39.8)  ; their  valence  is  one,  and  therefore  their 
atomic  weight  the  same  as  their  equivalent  weight.  For  the 
magnesium  group  (39.9),  the  corresponding  product  has  to  be 
doubled,  hence  the  valence  is  2,  and  the  atomic  weight  twice 
their  equivalent  weight.  For  aluminium  and  gold  (39.10)  the 
product  has  to  be  trebled  to  make  it  equal  to  6.4;  hence  the 
valence  is  3,  and  the  atomic  weight  three  times  the  equivalent. 
For  carbon  the  valence  is  4. 

6.  In  this  manner  we  obtain  the  following  preliminary  table 
of  atomic  weights,  arranging  the  metals  vertically  according 
to  their  electro-chemical  character  first,  their  valence  next, 
and  in  each  line  according  to  the  magnitude  of  their  atomic 
weight.  The  metals  in  each  line  form  a group  or  GENUS, 
designated  by  name  and  Greek  symbol,  essentially  as  in  my 
Atomechanics  of  1867. 

Since  carbon  forms  the  natural  center  of  this  group,  we  shall 
call  this  the  carbon  system  of  metals — the  metals  predominat- 
ing in  number. 


7.  THE  CARBON-SYSTEM  OF  VOLATILE  METALS,  giving 
incrustation  on  charcoal. 


Electro. 

Val. 

Name. 

Sym. 

ISt. 

2nd. 

3id. 

4th. 

Sth. 

Positive, 

I. 

Kaloids, 

Ka 

Li 

7 

Na  27 

2. 

Cadmoids, 

Kd 

Be 

9 

Mg  24 

Zn  65.5 

Cd  112 

Hg  200 

3- 

Styptoids, 

2r 

Bo 

1 1 

A1  27 

Ga  70 

In  1 14 

T1  204 

Neutral, 

4- 

Adamantoids, 

, A4 

C 

12 

Si  28 

Ge  73 

Sn  118 

Pb  207 

3- 

Phosphoids, 

4) 

N 

H 

P 31 

As  75 

Sb  120 

Bi  208 

2. 

Sulphoids, 

0 

() 

i6 

8 32 

Se  79 

Te  124 

Negative, 

I. 

Chloroids, 

X 

FI 

19 

Cl  35-5 

Br  80 

lo  127 

ATOMS  AND  MOLECULES. 


201 


Secondary,  lighter,  earth -forming  groups: 

Positive,  i.  Kaloids,  Ka  Ku  39  Rb  85  Cs  132 

2.  Calcoids,  Xa  Ca  40  Sr  88  Ba  137 

The  kaloids  are  the  most  strongly  electropositive,  the 
chloroids  the  most  strongly  electronegative ; the  intermediate 
groups  are  electrically  intermediate.  Compare  36,  7. 

8.  A corresponding  group  of  non-volatile  metals,  giving 
NO  INCRUSTATION  ON  CHARCOAL  and  less  plainly  charac- 
terized in  valence,  may  be  called  the  IRON  SYSTEM  OF 
METALS.  Increase  of  atomic  weight  increases  the  electro- 
positive character  (contrasting  with  carbon  system). 

Most  Va 


Negative, 

Moljbdoids, 

Cr  52 

Mn  55 

Mo 

96 

Wo 

185 

Sideroids, 

Fe  56 

Ni  58 

Ru 

104 

Ir 

193 

Palladoids, 

Co  59 

Pd 

106 

Pt 

194 

Positive, 

Cuproids, 

Kv 

Cu  63.5 

Ag 

108 

Au 

197 

9.  The  atomic  weights  here  given  are  used  in  the  calcula- 
tion of  analyses  and  in  the  preparation  of  solutions  and  com- 
pounds. The  terms  milligramme-atom  and  gramme-atom  are 
readily  understood;  a mgr. at.  is  the  number  of  milligrammes 
equal  to  the  atomic  weight.  Thus  a mgr. at.  of  silver  is  108 
mgr.  silver,  and  a gr.at.  sulphur  is  32  grammes  of  sulphur. 

10.  A MOLECULE  is  the  smallest  number  of  atoms  form- 
ing a physical  system,  moving  as  a single  body. 

IN  THE  GASEOUS  STATE,  and  under  the  same  temperature 
and  pressure,  the  molecular  volume  of  all  substances  is  the 
same  (LAW  OF  AVOGADRO,  1811). 

The  practical  unit  of  weight  being  the  milligramme,  the 
mgr.  molecular  volume  of  any  substance  in  the  gaseous  state 
is  the  number  of  cc  occupied  by  2 mgr.  of  hydrogen  gas. 

11.  This  law  gives  a ready  means  for  the  DETERMINATION 
OF  THE  MOLECULAR  WEIGHT  of  volatile  substances  by 
methods  resembling  specific  gravity  determinations.  It  is  only 
necessary  to  determine  the  volume  v in  cc,  occupied  by  a 
known  weight,  w mgr.  Under  the  same  conditions  of  tem- 
perature and  pressure,  24  mgr.  Mg.  yield  q cc  hydrogen  gas. 


202 


LECTURE  40. 


to  be  determined  by  direct  experiment  (38,  9).  Hence  the 
V cc  gas  represent  v divided  by  q mgr.  molecules;  let  this 
number  be  n.  Then  the  weight  w,  is  n mgr.  molecules,  each 
one  molecule  therefore  weighs  w divided  by  n. 

12.  Such  determinations  constitute  an  essential  part  of  all 
laboratory  work.  It  is  carried  out  by  means  of  my  gas 
burettes,  with  or  without  air  lock,  and  also  by  the  Victor 
Meyer  displacement  apparatus. 

Experiments  show  that,  as  for  hydrogen,  so  for  oxygen, 
nitrogen  and  chlorine,  also  for  vapors  of  bromine  and  iodine, 
the  molecule  consists  of  two  atoms.  For  water,  carbon  dioxide 
and  other  gases  obtained  by  synthesis,  the  molecule  consists 
of  one  atom  only,  such  as  H2O;  CO2. 


Notes.  That  chemical  compounds  differ  from  mixtures  in  having 
their  constituents  united  in  fixed,  definite  proportions,  was  more  or  less 
understood  over  a century  ago.  The  investigations  of  Wenzel  and 
especially  Richter  (p.  33)  on  neutral  salts  and  the  combining  propor- 
tions of  acids  and  bases,  made  this  clear.  It  was  however,  drawn  in 
question  by  no  less  a chemist  than  Berthollet  (p.  32),  but  settled  against 
him  by  Proust. 

Dalton  (p.  32),  comparing  the  different  oxides  of  metals  and  a few 
gases  as  to  composition,  found  that  all  facts  known  could  be  expressed 
by  saying:  substances  combine  in  fixed,  simple  multiple  pro- 
portions BY  WEIGHT.  Being  a thinker,  as  well  as  a chemist,  he  con- 
ceived the  idea  of  limited  particles  of  matter,  each  kind  having  a definite 
weight  of  its  own;  such  particles  would  combine  only  in  fixed  and  simple 
multiple  proportions  For  the  name  of  these  particles  he  revived  the 
term  atom  from  the  old  Greek  philosophers,  who  thereby  designated  the 
final,  indivisible  particles  of  matter. 

Independent  of  all  philosophical  speculation,  the  chemical  atom,  as 
defined  by  us,  is  as  real  as  matter  itself.  The  chemical  atom  is  rela- 
tively INDIVISIBLE,  that  is,  in  reference  to  the  substance  which  is  com- 
posed of  these  atoms.  Atoms  of  water  are  indivisible  as  such;  for  if 
divided,  water  ceases  to  be  constituted  by  them;  we  have  only  atoms  of 
the  constituent  hydrogen  and  oxygen. 

This  idea  of  relative  indivisibility  is  not  restricted  to  chemistry,  but  is 
quite  general.  A book,  a flower,  an  animal,  also  are  as  indivisible  as  the 
atom — in  relation  to  the  kind  of  being  they  are.  In  other  words,  the 
final  philosophical  question  of  the  limited  divisibility  of  matter  in  gen- 
eral is  not  part  of  the  question  of  the  reality  of  chemical  atoms. 

A certain  prominent  modern  chemist  denies  the  reality  of  chemical 
atoms — but  he  also  denies  the  reality  of  matter.  A chemist  denying 
matter  is  exclusively  a modern  phenomenon. 


41.  ELEMENTS  AND  COMPOUNDS. 


1.  We  have  begun  the  study  of  chemistry  proper  with  the 
study  of  THE  METALS.  This  well  defined  and  most  im- 
portant class  of  bodies  also  formed  the  starting  point  for  the 
chemists  of  old.  For  about  a century,  this  natural  and  to  all 
familar  group  of  bodies,  has  been  put  into  the  back  ground  by 
chemists.  We  deliberately  have  begun  our  course  in  chemistry 
with  the  substance  rather  than  with  the  shadow. 

2.  We  have  also  noted  a class  of  bodies  called  non-metals, 
comprising  sulphur,  carbon,  iodine.  To  this  group  we  after- 
wards added  the  noted  gases  hydrogen,  oxygen,  nitrogen  and 
chlorine.  These  bodies  combined  with  the  metals,  forming 
new  bodies,  chemical  compounds.  By  heat,  and  notably  by 
electricity,  we  have  decomposed  these  compounds,  reproducing 
the  original  metal  at  the  negative  electrode,  and  recognizing 
the  non-metals  as  electro -negative  substances. 

3.  Looking  at  the  grouping  of  the  metals  in  40,  7 and 
and  8,  we  are  struck  with  the  MANY  RELATIONSHIPS  brought 
to  our  mind  in  tracing  the  lines  from  right  to  left,  following 
the  species  of  a genus  with  increasing  atomic  weight,  or  up 
and  down,  according  to  varying  valence  and  electrical  con- 
trast. They  look  not  at  all  like  independent  substances,  but 
rather  like  compound  bodies,  systematically  arranged  accord- 
ing to  their  composition. 

4.  Nevertheless  chemists,  the  world  over,  have  considered 
these  bodies  to  be  simple  substances,  not  compound.  Modern 
chemists  have  derided  their  predecessors  of  two  thousand  years, 
who  looked  upon  the  metals  as  compounds,  the  alchemists  even 
deliberately  trying  to  change  one  metal  into  another.  Are  the 
chemists  right  and  were  the  old  chemists  in  error?  Let  us 
examine  the  facts  without  prejudice. 

5.  The  principal  means  of  decomposition  at  hand  are 
increase  in  temperature  and  electrical  tension  and  current.  We 


204 


LECTURE  41. 


have  exemplified  the  use  of  both  these  powers.  Thus  far,  the 
metals  have  resisted  both  of  these  powers  under  all  conditions. 
They  clearly  form  a class  of  matter  different  from  ordinary 
compounds,  which  we  have  decomposed.  Hence,  they  ought 
to  be  designated  by  a distinctive  name.  We  properly  adopt 
their  common  name  CHEMICAL  ELEMENTS.  The  non-metallic 
elements  are  commonly  called  METALLOIDS. 

6.  But  the  definition  of  this  term  should  be  in  accordance 
with  fact.  A CHEMICAL  ELEMENT  IS  A SUBSTANCE  THAT 
HAS  NOT  BEEN  DECOMPOSED.  To  say  that  it  CANNOT  be 
decomposed  would  be  to  assert  that  those  who  succeed  us  will 
be  limited  by  our  powers  and  our  knowledge.  Such  assertions 
are  manifestly  unwarranted  and  unscientific.  History  has 
often  proved  them  to  be  false. 

7.  As  to  volume  in  the  gaseous  state,  the  elements  deport 
themselves  exactly  as  compounds.  The  molecular  volume  is 
the  same  for  all.  There  is  no  difference  whatever  in  this 
most  fundamental  relation  between  the  elements  and  com- 
pounds. 

8.  As  to  specific  heat  there  is  a radical  difference.  Berth - 
elot  has  first  recognized  and  formulated  it  (1873).  The 
specific  heat  of  an  atom  of  any  chemical  element  is  the  same 
(39),  entirely  independent  of  the  weight  of  that  atom,  though 
this  weight  varies  from  1 to  over  200!  But  for  a series  of 
compounds,  resembling  one  another,  the  specific  heat  of  the 
compound  atom  is  almost  directly  proportional  to  the  atomic 
weight. 

9.  1 have  shown  that  there  is  also  a radical  difference  be- 
tween the  effect  of  the  SUBSTITUTION  of  an  element  and  a 
compound  on  the  properties  produced  (1892).  In  certain 
simple  organic  compounds  called  PARAFFINS,  one  hydrogen 
atom  may  be  replaced  by  an  atom  of  FI,  Cl,  Br,  lo  or  Cyan- 
ogen, which  is  Cy  — CN,  a compound  radical  of  the  atomic 
weight  2G.  The  boiling  point  increases  with  the  atomic 
weight  of  the  elements  in  these  substitutions,  as  shown  in 


ELEMENTS  AND  COMPOUNDS. 


205 


the  diagram,  page  77.  Here  Cy  is  at  the  top,  showing  the 
greatest  increase,  more  than  for  Io=127;  in  fact,  for  an  ele- 
ment it  would  require  an  atomic  weight  of  150.  Yet  the  rad- 
ical has  only  the  atomic  weight  26. 

10  Both  of  these  striking  differences  between  elements 
and  compounds  were  fully  accounted  for  on  mechanical  prin- 
ciples in  my  notes  presented  by  Berthelot  to  the  Academy  of 
Sciences  of  Paris  (1892).  The  conclusion  is  not,  that  the 
elements  are  really  simple  bodies,  but  that  the  constituent 
particles  of  their  atoms  are  at  relatively  small  distances,  as 
compared  to  the  relatively  great  distances  of  the  element 
atoms  in  ordinary  compounds. 

11.  Thus  the  question  as  to  the  simple  or  composite  nature 
of  the  chemical  element  stands  in  the  following  position.  No 
chemical  element  has  thus  far  been  actually  decomposed ; 
the  observations  of  Lockyer  (1879)  and  Crookes  do  not  war- 
rant the  conclusion  drawn  by  these  scientists.  But  at  the 
same  time,  not  a single  fact  is  known  proving  or  indicating 
that  the  elements  are  not  composite  substances;  on  the  con- 
trary, their  mutual  relationship,  exhibited  in  the  tables  (40, 
7,  8).  showing  their  properties  to  vary  with  weight  and  val- 
ences, is  a positive  indication  of  their  being  compounds. 

12.  The  pretended  exact  atomic  weights  of  Stas  (p.  33) 
are  commonly  considered  to  prove  that  the  elements  cannot  be 
compound  bodies;  but  these  data  have  been  shown  to  be 
erroneous  in  my  communications  to  the  Academy  of  Sciences 
of  Paris  and  in  my  True  Atomic  Weights,  1894.  The  values 
of  Stas  are  not  constant,  but  vary  with  the  amount  of  sub- 
stance used.  See  p.  79.  In  this  work,  the  so-called  “Peri- 
odic Law  ” of  the  common  text  books  is  also  examined. 

The  first  extended  publication  on  the  natural  classification 
and  cofnposite  nature  of  the  elements  was  made  in  my 
Programme  of  Atomechanics,  1867. 


42.  ALLOTROPY  AND  ISOMERY. 


1.  The  three  substances  charcoal,  graphite  and  the  dia- 
mond, have  been  known  to  man  from  very  early  times. 
They  are  as  different  from  one  another  as  any  other  three 
bodies  possibly  could  be.  No  chemist  suspected  these  bodies 
to  be  related  in  any  way,  until  in  modern  times.  The  trans- 
parent and  most  valuable  gem  (10,  12),  the  marking  substance 
of  our  pencils,  and  the  charred  remains  of  wood,  seemed  to 
be  bodies  entirely  unrelated. 

2.  Nevertheless,  these  three  bodies  are  hot  only  related, 
but  they  are  chemically  one  and  the  same  element  carbon,  in 
three  different  (ALLOTROPIC)  states  or  conditions.  Berzelius 
coined  the  word  used;  it  explains  nothing,  only  fixes  in  our 
mind,  by  a special  term,  a special  set  of  facts.  Other 
elements,  especially  S,  P,  O also  show  allotropy. 

3.  The  following  properties  are  common  to  all  forms  of 
carbon,  and  thus  characterize  the  SPECIES  of  matter  chemists 
designate  by  the  symbol  C : Solid,  infusible  and  non-volatile 
in  the  highest  heat  of  our  furnaces,  but  volatilizing  (boiling?) 
in  the  electric  arch;  combustible,  at  least  in  pure  oxygen,  at  a 
red  heat,  yielding  eleven -thirds  of  its  own  weight  of  carbon 
dioxide  gas  and  nothing  else;  it  is  insoluble  in  all  ordinary 
solvents,  but  dissolves  readily  at  the  highest  temperatures 
(electric  furnace)  in  many  molten  metals. 

4.  That  even  the  DIAMOND  IS  COMBUSTIBLE,  was  first 
suspected  by  Newton  (1740),  because  of  its  high  refractive 
power.  The  combustion  of  the  diamond  was  first  effected  in 
oxygen  by  Lavoisier,  who  thus  established  its  true  chemical 
nature.  The  TEMPERATURE  OF  IGNITION  varies  greatly 
with  the  form  of  carbon.  Certain  charcoals,  made  of  willow 
wood  at  low  heat,  ignite  at  correspondingly  low  temperatures 
and  are  used  for  gunpowder.  Graphite  and  diamond  do  not 
burn  even  in  oxygen  until  at  a bright  red  heat. 


ALLOTROPY  AND  ISOMERY. 


207 


5.  Carbon  dissolved  in  molten  iron  (cast  iron  contains 
5 per  cent.)  may  crystallize  on  cooling.  This  form  is  invari- 
ably GRAPHITE,  soft,  readily  marking  paper  and  wood 
(pencils),  G 2.2  and  rhombohedral.  When  such  a carbon 
solution  in  iron  is  suddenly  chilled  on  the  surface,  to  solidifica- 
tion, the  interior  is  compressed  by  the  shrinking  of  the  solid 
crust,  and  the  carbon  crystallizes,  under  this  high  pressure, 
as  DIAMOND  (Moissan). 

6.  The  various  common  forms  or  VARIETIES  OF  CARBON, 
both  mineral  and  artificial,  have  been  sufficiently  indicated. 
See  5,  2.3;  10,  12;  12,  10.  Bituminous  coals,  when  heated 
in  a retort  or  oven,  leave  a COKE,  corresponding  to  the-char- 
coal  left  by  wood  under  like  conditions.  Resinous  substances 
yield  lamp  black,  the  lightest  form  of  carbon.  Bones  give 
animal  charcoal,  the  noted  absorbent  for  color  and  other 
matters.  The  volatile  portion  of  bituminous  coals,  purified,  is 
illuminating  gas.  • 

7.  PHOSPHORUS  also  presents  itself  in  two  allotropic  con- 
ditions, namely  ordinary  amber  colored  and  red  phosphorus. 
By  keeping  ordinary  phosphorus  heated  to  240  degrees  for  ten 
days  continuously,  it  is  converted  into  the  red  modification. 
To  remove  the  small  parts  of  the  common  (poisonous)  phos- 
phorus from  the  red  (non-poisonous)  modification,  the  cold 
mass  is  treated  with  bisulphide  of  carbon,  which  dissolves  the 
common  and  not  at  all  the  red  phosphorus. 

8.  The  following  additional  contrasting  properties  are 
worthy  of  notice.  The  property  first  given  applies  to  common 
phosphorus;  the  corresponding  property  of  the  red  modifica- 
tion is  put  into  parenthesis. 

Specific  gravity,  1.83  (1.9G).  Phosphorescent  on  surface 
(not).  Inflammable  at  60  degrees  (230  degrees) . Violently 
attacked  by  nitric  acid  (only  slightly  attacked  when  heated), 
making  this  a dangerous  reaction  (comparatively  safe). 
Crystallizes  at  common  temperatures  (at  580  degrees). 

9.  SULPHUR  also  exhibits  allotropic  modifications.  Its 
dimorphism  has  been  fully  presented  (21,  6.7).  When  limpid 


208 


LECTURE  42. 


melted  sulphur  (113  to  120  degrees)  is  heated  to  about  200 
degrees,  it  becomes  viscid ; above  that  temperature  it  again 
becomes  a limpid  liquid.  The  viscid  sulphur  (at  230)  poured 
into  water,  stays  soft  for  a long  time,  and  is  used  for  taking 
molds. 

10.  OXYGEN  GAS  under  the  influence  of  electrical  dis- 
charges— even  in  electrolysis  (37.7) — changes  to  ozone,  the 
more  active  form  of  oxygen.  Silver  is  not  attacked  at  common 
temperatures  by  pure,  dry  oxygen ; ozone  promptly  blackens 
it.  The  density  of  ozone  is  50  per  cent,  in  excess  of  that  of 
oxygen;  that  is,  while  oxygen  gas  has  the  molecules  O2, 
those  of  ozone  are  O3 . Ozone  readily  reverts  to  oxygen;  a 
moderate  heating  is  sufficient  for  this  change. 

11.  A chemical  compound  existing  in  two  or  more  physically 
different  forms  is  called  ISOMERIC.  Thus  mercuric  iodide 
shows  two  isomeric  forms,  the  red  and  the  yellow  (23,  7.8). 
Mercuric  sulphide,  precipitated  from  its  solutions  by  hydrogen 
sulphide,  is  black  (22,  8 and  notes).  By  heating,  this  black 
sulphide  changes  to  a red  sublimate,  cinnabar.  White  arsenic 
crystallizes  on  a hot  surface  prismatic,  on  a cold  surface  octa- 
hedral ; on  a very  hot  surface  it  condenses  to  a vitreous  mass, 
which  gradually  turns  opaque  like  porcelain. 

12.  The  phenomena  of  allotropy  and  isomery  must  evi- 
dently be  carefully  considered  when  the  nature  of  the  elements 
is  to  be  investigated.  Dimorphism  may  be  looked  upon  as  the 
expression  of  two  positions  of  equilibrium,  as  already  demon- 
strated in  my  programme  of  1867.  Allotropy  is  probably  also 
dependent  on  the  formation  of  more  complex  molecules,  by  the 
grouping  of  more  atoms,  as  is  plainly  proved  in  the  case  of 
oxygen  and  ozone. 


43.  BINARIES  AND  TERNARIES. 


1.  Two  elements  combining,  form  a binary  compound; 
three  elements  united,  form  a ternary  compound.  But  nearly 
all  compounds  being  DUAL,  as  we  have  seen  quite  early  in 
the  course,  and  as  has  been  confirmed  by  electrolysis,  we 
more  properly  look  upon  compounds  as  containing  TWO  con- 
stituents only,  one  or  both  of  which  may  be  compound 
radicals.  Lect.  31. 

2.  The  electropositive  constituent  of  a compound  is  a metal 
(in  salts)  or  hydrogen  (in  acids) ; the  metal  and  hydrogen 
being  interchangeable  by  substitution.  If  therefore,  the 
FORMULA  OF  THE  ACID  be  given  or  remembered,  it  is  easy 
to  state  the  formula  of  the  corresponding  salt,  provided  the 
valence  of  the  metal  be  known.  Substitution  taking  place, 
not  atom  for  atom,  but  equivalent  (i.  e.  unit  of  valence)  for 
equivalent. 

3.  For  example,  the  formula  of  hydrochloric  acid  or  HYDRO- 
GEN CHLORIDE  is  H Cl ; both  constituents  being  monovalent, 
the  atomic  and  equivalent  formula  are  identical.  Now  Ag 
being  monovalent,  Ag  CL^e  will  be  expressed  by  the  formula 
Ag  Cl.  But  zinc  is  divalent,  hence  its  chloride  has  the  formula 
Zn  CI2.  Bismuth  being  trivalent,  its  chloride  is  represented 
by  the  formula  Bi  Cl  3.  The  number  of  monovalent  negatives 
must  equal  the  valence  of  the  positive  constituent. 

4.  If  now  instead  of  Cl  we  have  any  other  chloroid,  the 
formula  will  remain  the  same,  only  the  second  symbol  will 
change.  Thus  silver  fluoride  Ag  FI.  Zinc  bromide  Zn  Bi'a. 
Bismuth  iodide  Bi  I03.  These  are  all  binaries  proper.  Even 
the  radical  cyanogen,  Cy  or  CN  gives  compounds  of  this 
structure  and  named  like  a binary,  cyanide.  Thus  Ka  Cy 
represents  potassium  cyanide,  Ba  Cyo  barium  cyanide. 

5.  If  instead  of  starting  with  hydrogen  chloride,  we  start 
with  NITRIC  ACID,  H N^te,  the  formula  of  which  is  H O3N,  we 
still  can  write  the  formula  as  before,  for  NlTRATpS  ARE  DUAL 
COMPOUNDS,  CONTAINING  THE  MONOVALENT  RADICAL 


210 


LECTURE  43. 


O3N  AS  ELECTRO  NEGATIVE.  Thus  silver  nitrate  has  the 
formula  Ag  O3N;  barium  nitrate  Ba  (03N)2,  bismuth  nitrate 
Bi  (03N)3. 

Chlorates  correspond  exactly  to  nitrates.  Thus  KaCl^te 
has  the  formula  Ka  O3CI;  BaCl^te  is  Ba  (0301)2. 

6.  OXIDES  are  binaries  containing  the  divalent  electro- 
negative ELEMENT  oxygen.  The  formulae  H2O,  Ba  O,  Ka20, 
Zn  O,  CO2,  Si  O2  are  perfectly  normal,  the  valence  of  the 
negative  balancing  that  of  the  positive  constituent.  For 
phosphoids,  to  avoid  fractions,  we  write  P2O3;  but  this  in- 
volves a question,  which  we  must  leave  untouched  at  present. 

Sulphides  correspond  exactly  to  oxides;  Zn  S,  C S2,  Ba  S. 

7.  SULPHATES  correspond  also  to  oxides,  containing  the 
DIVALENT  RADICAL  O4S  instead  of  oxygen;  our  S^te  is 
=04S.  Thus  the  formula  of  sulphuric  acid  is  written  H2O4S ; 
Ba  Sate  is  Ba  O4S.  Potassium  sulphate  Ka204S.  Zinc  sul- 
phate Zn  O4S. 

Chromates  contains  the  divalent  radical  04Cr,  SUL- 
PHITES the  divalent  radical  O3S.  Consequently  lead  chro- 
mate is  Pb  04Cr  and  calcium  sulphite  Ca  O3S. 

CARBONATES  contain  the  divalent  radical  O3C.  Hence 
zinc  carbonate  Zn  O3C. 

8.  NITRIDES  contain  the  trivalent  element  nitrogen  as 
negative.  The  most  important  nitrides  are  those  of  the  triva- 
lent phosphoid  group.  For  example,  ammonia  H3N,  phos- 
phuretted  hydrogen  H3P,  arseniuretted  hydrogen  H3  As. 

The  nitrides  of  the  chloroid  group  are  all  explosive.  Thus 
N CI3  is  perhaps  the  most  explosive  of  all  substances. 

9.  PHOSPHATES,  normal,  contain  the  TRIVALENT  RADI- 
CAL O4P;  hence  their  formula  may  be  written  exactly  as  that 
of  a nitride.  The  acid  is  H3  O4P.  Potassium  phosphate 
Kas  O4P. 

ARSENATES  correspond  to  the  phosphates.  H3  O4AS  is 
arsenic  acid,  Ag3  O4P  represents  normal  silver  phosphate. 

It  is  not  necessary  to  give  cases  of  tetravalence  at  this  place. 
They  will  be  understood  when  they  occur. 


BINARIES  AND  TERNARIES. 


211 


10.  It  is  evident  that  for  example,  in  sulphates,  the  two 
hydrogen  atoms  of  the  acid  need  not  both  be  replaced  by  a 
metal;  in  that  case  we  obtain  a so-called  ACID  SALT,  com- 
monly designated  by  the  prefix  bi — . Thus  H2  O4S,  HKa 
O4S  and  Ka2  O4S  represent  H S^te,  Ka  bisulphate  and  Ka 
Sate.  The  same  terminology  is  applied  to  carbonates  and  sul- 
phites. Thus  HKa  O3C  represents  Ka  bicarbonate,  and 
HNa  O3S  represents  Na  bisulphite. 

11.  For  the  TRIVALENT  RADICALS,  such  as  O4P  of  phos- 
phates, the  three  valencies  H3  may  be  represented  by  KaH2, 
KasH  or  Kas ; such  salts  are  termed  monopotassic,  dipotassic 
and  tripotassic  phosphate.  But  also  metals  of  other  valence 
may  enter.  Thus  the  crystallized  ammonio-magnesium  phos- 
phate, precipitated  from  alkaline  solutions,  is  O4P  + 6 H2O. 
The  trivalent  radical  is  saturated  by  the  divalent  Mg  and  the 
monovalent  ammonium  Am.  In  the  so-called  microcosmic 
salt,  the  three  valencies  are  represented  by  one  atom  each  of 
sodium,  ammonium  and  hydrogen;  the  salt  contains  four 
atoms  of  water  of  crystallization.  Write  the  formula. 

12.  These  general  rules  and  special  examples  may  suffice 
for  the  understanding  of  the  writing  and  reading  of  chemical 
formula.  The  common  (now  atomic)  formula  represent  one 
atom  of  the  compound.  The  positive  is  generally  a metal  or 
hydrogen.  The  electro -negative  is  an  element  (in  binaries) 
or  a radical  (in  ternaries).  It  is  the  valence,  that  is,  the 
number  of  equivalents,  that  must  balance  in  the  formula  as  in 
the  compound. 

The  more  general  group  formulas  (Greek  symbols  of  genera) 
given  already  in  our  Atomechanik  1867,  can  only  be  mentioned 
here.  These  general  formula  are  also  used  in  our  treatise  on 
the  statistics  of  crystal  symmetry  in  the  transactions  of  the 
Academy  of  Sciences  of  Vienna  for  1870. 


Notes.  A practical  difficulty  in  the  writing  of  chemical  formulae 
must  yet  be  cleared  up.  We  may  say,  in  general,  that  the  metals  also 
occur  combined,  forming  radicals. 


212 


LECTURE  43. 


Thus  mercury  is  considered  divalent — in  the  mercuric  series  of  com- 
pounds. But  in  mercurous  compounds^  we  must  consider  two  atoms  of 
mercury  combined  to  form  the  divalent  radical  Hg2. 

Again,  ferrous  compounds  contain  one  atom  of  iron  combined  with 
only  two  valencies  of  the  negative;  it  is  said  that  ferrous  compounds  are 
NOT  SATURATED.  When  oxidized  to  ferric,  the  iron  radical  Fe2  has 
formed,  with  a valence  6.  Ferric  chloride  contains  2 Fe  as  positive  and 
6 Cl  as  negative.  Ferric  sulphate  contains  the  hexvalent  Fea  saturating 
three  divalent  radicals  O4S. 

In  like  manner,  the  tetravalent  Pt  forms  two  series  of  compounds,  the 
PLATiNic  and  PLATINOUS.  The  first  are  considered  normal,  each  Pt 
being  combined  with  four  equivalents  (valencies)  of  the  negative  element 
or  radical.  In  the  platinous.  each  Pt  is  combined  with  two  such  valen- 
cies only;  these  compounds  are  spoken  of  as  non-saturated. 

In  the  same  manner  we  have  Stannous  (non-saturated)  and  Stannic 
(saturated)  compounds. 

Fixed  air,  carbon  dioxide,  is  considered  saturated  COg  ; four  valen- 
cies or  equivalents  of  the  positive  carbon  being  united  with  two  divalent 
oxygen  atoms.  But  carbonic  oxide  is  CO  ; it  is  considered  non-saturated, 
but  acts  quite  like  a neutral  body. 

These  few  remarks  have  been  added  only  to  deal  with  the  practical 
points  involved  in  the  writing  and  reading  of  chemical  formulae,  not  to 
solve  difficulties  in  valence. 

Constitution  of  Ternaries.  The  author  wishes  it  distinctly  under- 
stood that  ALL  the  detail  given  even  in  elementary  text  books  on  this 
subject  is  unreliable,  useless  and  misleading;  much  thereof  is  in  conflict 
with  crystallographic  facts  now  commonly  disregarded.  Deeming  it 
improper,  in  a text  book,  to  teach  anything  untrue  and  in  conflict 
with  fact,  all  elegant  structural  formuhe  of  ternaries  are  deliberately  ex- 
cluded from  this  work. 

What  has  been  given  on  their  constitution  is  perhaps  both  new  and  old — 
new  in  not  being  found  in  the  books  of  the  day,  and  old  in  being  conform 
to  the  representations  of  an  earlier  day;  but  it  has  two  good  reasons  for 
a place  in  this  text  book,  namely  it  is  strictly  conform  to  chemical  and 
electrolytical  phenomena,  and  does  not  go  beyond  the  solid  basis  of 
experience. 

Name  of  Ternaries.  The  ending  is  in  t,  indicating  three  elements 
combined ; the  connecting  vowel  is  a for  common,  i for  a less  amount  of 
oxygen.  In  English,  a final  e is  added  to  the  t.  Thus  we  have  iron  sul- 
phate and  sulphite. 

The  ternaries,  with  more  oxygen  than  the  .\te,  take  the  prefix  per, 
those  with  less  than  ites  take  iivpo  before  the  negative.  Thus  perchlor- 
ates and  hypochlorites. 

If  intermediate  element  of  ternary  be  not  oxygen  (understood  in  pre- 
ceding), then  root  of  name  must  be  inserted.  Thus  Ka  S-As’te  is  potas- 


FORMULA  AND  COMPOUND. 


213 


sium  sulph-arseiiite ; Am  Cl-Pt^ife,  ammonium  chloro-platinate.  As 
intermediate  occur  mainly  O,  S;  FI,  Cl,  Br,  lo.  Cy.  Yellow  prussiate  is 
Ka  Cyo-Fe5i‘e,  red  prussiate  Ka  Cy'-Fe^^^e;  Cy»  reads  cyano — , and  Cy> 
reads  cyani. 


44.  FORMULA  AND  COMPOUND. 

1.  We  have  now  exposed  all  the  essential  principles  on 
which  the  MODERN  CHEMICAL  FORMULA  are  constructed. 
We  have  also  given  a sufficient  number  of  examples  to  make 
the  practice  of  writing  such  formulae  reasonably  easy.  We 
regret  the  necessity  of  words  of  warning  against  the  almost 
universal  ABUSE  of  these  formula. 

2.  The  student  should  always  bear  in  mind,  that  the 
CHEMICAL  FORMULA  of  a compound  IS  NOT  THE  COM- 
POUND itself.  The  name  is  not  the  thing.  The  word  is  not 
the  object.  And  yet  it  is  a fact,  that  in  lecture  halls  and 
laboratories,  in  books  and  periodicals,  the  chemical  formula  is 
made  much  more  prominent  than  the  chemical  substance,  or 
its  reactions  and  properties. 

3.  The  chemical  formula,  if  correct,  is  merely  a symbolic 
representation  of  one  atom  of  the  chemical  compound.  Above 
all,  it  is  applicable  only  to  substances  sufficiently  pure,  never 
to  crude  materials.  To  refer,  by  chemical  formulae,  to  crude 
acids  and  ordinary  chemicals,  is  false  in  every  sense  of  the 
word.  Such  a practice  does  not  show  learning,  but  proclaims 
ignorance. 

4.  To  avoid  such  practice,  we  have  from  an  early  day  used 

the  simple  abbreviation  of  the  chemical  names  now  familiar  to 
the  student.  H more  brief  than  the  name  hydrogen 

sulphate  or  sulphuric  acid;  it  represents  the  actual  DUAL 
nature  of  the  compound  which  must  be  known  to  understand 
its  reactions;  it  does  not  hide  the  chemical  essence  under  a 
string  of  letters  or  symbols  such  as  H2O4S. 


214 


LECTURE  44. 


5.  Unless  the  radical  is  broken  up  in  an  exceptional  re- 
action, it  acts  like  one  thing,  like  an  element  atom;  and  any 
expression  hiding  that  fact,  hides  the  mechanism  of  the 
chemical  reaction,  hides  that  which  we  try  to  feach  or  to  learn. 
Besides,  it  does  not  put  an  undue  strain  on  the  memory,  and 
thus  gives  the  mind  a chance  to  think  of  the  essential  clearly. 

6.  Again,  intricate  formulas,  supposed  to  represent  re- 
actions, are  written  on  blackboards,  and  printed  in  books,  for 
students  to  learn ; and  yet  these  formulas  are  not  true,  and  the 
reactions  will  not  take  place  at  all,  if  the  materials  are  taken 
strictly  conform  to  these  formulas.  The  chemical  process 
learnedly  represented  will  simply  not  proceed.  Such  are,  for 
example,  the  long  equations  expressing  the  volumetric  re- 
actions of  potassium  permanganate  with  oxalic  acid  and 
ferrous  salts. 

7.  As  we  shall  not  burden  these  pages  with  such  formulae 
ourselves,  and  as  the  lesson  has  to  be  brought  home,  we  insert 
the  formulae  referred  to,  exactly  as  they  are  found  in  the  books. 

2 K Mn  O4  + 5 H2C2O4  + 3 H2SO4  = K2SO4  + 2 Mn  SO4 

+ 10  CO2  + 8 H2O. 

10  Fe  SO4  + 2 K Mn  O4  + 8 H2SO4  = K2SO4  + 2 Mn  SO4 
+ 5 Fe2  (804)3+8  H2O. 

Now,  if  you  will  take  precisely  these  quantities,  the  reaction 
will  not  take  place  as  expressed — the  determination  attempted 
will  be  a miserable  failure.  The  only  result  is  the  bewilder- 
ing of  the  student.  The  real  mechanism  of  the  simple 
chemical  reaction  is  completely  obscured  by  a cloud  of  irrele- 
vant and  false  details. 

8.  PERMANGANATE,  Ka  04Mn,  was  first  produced  (1820) 
and  applied  by  my  teacher  in  chemistry.  Professor  Forch- 
hammer  of  Copenhagen.  In  the  presence  of  oxidable  ma- 
terials, AND  A LARGE  EXCESS  OF  SULPHURIC  ACID,  it 
breaks  up,  the  Mn  forming  ordinary/  compounds  as  electro- 
positive. Now,  the  only  and  the  essential  thing  to  know,  is 
that  2 permanganate  will  yield  one  Ka20  and  2 MnO,  the 
excess  of  acid  attends  to  keeping  them  in  solution.  But  this 


FORMULA  AND  COMPOUND. 


215 


accounts  for  3 of  the  8 oxygen ; hence  5 oxygen  are  set  free 
to  do  the  work  wanted  done. 

9.  The  effect  of  this  oxygen  on  the  oxidable  matter  is 
equally  simple.  The  ferrous  FeO  becomes  ferric,  FeaOg; 
or  2 ferrous  require  one  oxygen  to  become  ferric,  which  is 
kept  in  solution  by  the  large  excess  of  acid.  The  five  oxygen 
from  two  permanganate  will  therefore  oxidize  ten  ferrous;  that 
is,  ONE  PERMANGANATE  OXIDIZES  FIVE  FERROUS.  This 
gives  the  numerical  relation  wanted.  By  the  way,  the  long 
equation  is  still  too  short;  green  vitriol  should  have  been  re- 
placed by  hydrated  ammonio -ferrous  sulphate,  which  is  the 
true  standard.  See  the  blackboard  diagram. 

10.  The  books  should  be  freed  of  such  useless,  complex 
and  incorrect  show  of  chemical  learning  which  only  perplexes 
and  misleads  the  student.  For  one,  the  author  will  no  more 
introduce  such  sham  chemistry  in  this  textbook  than  he  allows 
it  in  his  laboratory.  We  endeavor  to  study  the  actual  process 
in  its  essential  and  determining  features,  even  if  we  lose  the 
appearance  of  learning. 

11.  To  give  chemical  formula,  when  asked  to  describe  a 
chemical  compound,  is  not  giving  an  answer  at  all.  The 
characteristic  properties  of  the  substance  determine  its  nature, 
and  not  the  formula.  It  is  the  substance  we  prepare,  test 
and  use,  not  the  formula.  The  substance  may  cure  disease, 
the  formula  can  not  do  that.  Compounds  are  not  marked  by 
nature  with  chemical  formulae,  but  by  properties;  it  is  by  these 
that  we  have  to  distinguish  them. 

12.  The  abuse  of  formulae  is  especially  out  of  place  at  the 
laboratory  stand  in  qualitative  analysis.  The  chemists  of  the 
present  have,  under  a new  name  it  is  true,  returned  to  the 
dualistic  Berzelian  constitution  of  compounds,  always  retained 
by  the  author,  and  expressed  in  his  simple  signs.  These  two 
constituents  determine  the  reactions;  the  complete  formula 
only  hides  it  from  the  eyes. 


45.  PURITY  AND  STRENGTH. 


1.  A chemical  compound  should  be  pure,  that  is,  contain 
nothing  but  what  its  name  implies  and  its  formula  indicates. 
But  such  absolute  purity  is  almost  impossible  to  procure;  only 
for  the  most  important  atomic  weight  determinations  is  an 
effort  made  to  reach  this  limit.  Commercial  products,  even  if 
marked  C.P.,  are  not  absolutely  pure. — See  True  Atomic 
Weights,  p.  140-142. 

2.  Although  it  may  be  extremely  difficult  to  secure  the 
highest  degree  of  purity,  it  is  comparatively  easy  to  prove 
the  presence  of  the  foreign  matter  or  impurity.  The  general 
methods  of  QUALITATIVE  CHEMICAL  ANALYSIS  (Lect.  22) 
form  the  basis  of  the  tests  for  impurities ; special  tests  of  great 
delicacy  are  sought  for  in  particular  cases.  We  shall  consider 
that  subject  soon. 

3.  Many  chemicals  it  is  impracticable  to  produce  in  the 
free  state;  they  are  sold  as  solutions  in  some  inert  solvent. 
This  is  the  case  with  most  acids  and  the  volatile  alkali,  which 
are  sold  in  aqueous  solution.  For  this  class  of  bodies,  it  is 
essential  that  nothing  but  the  chemical  and  the  inert  solvent 
be  present,  and  that  the  amount  of  the  active  substance  be 
not  below  the  per  cent,  stated.  Here  both  purity  and  strength 
are  required. 

4.  All  methods  for  the  determination  of  the  strength  of 
solutions  and  chemicals  in  general  belong  to  QUANTITATIVE 
CHEMICAL  ANALYSIS.  The  scientific  principles  involved  are 
subjects  proper  for  the  lecture  room,  though  the  details  of 
manipulation  and  the  minutiae  of  method  to  secure  most 
reliable  results  belong,  with  the  practice,  to  the  laboratory. 

5.  First  of  all,  these  quantitative  methods  may  be  distin- 
guished as  physical  and  chemical,  according  as  mainly  physi- 
cal processes  are  employed,  or  the  substance  submitted  to 
chemical  transformations  by  the  use  of.  reagents. 


PURITY  AND  STRENGTH. 


217 


6.  The  PHYSICAL  METHODS  of  determining  the  strength 
of  a given  chemical  consist  in  the  determination  of  the  so- 
called  PHYSICAL  CONSTANTS  of  the  substance,  such  as  the 
specific  gravity,  G;  the  fusing  point,  F;  the  boiling  point,  B; 
also  the  refracting  power;  the  rotation  of  the  plane  of  polariza- 
tion ; the  solubility  in  certain  neutral  solvents,  and  the  like. 
The  first  three  (G,  F,  B)  are  the  most  important. 

7.  There  are  two  methods,  depending  exclusively  on  phy- 
sical agencies,  but  accomplishing  chemical  changes  in  the  given 
substance;  namely  dissociation  and  electrolysis.  DISSOCIA- 
TION is  chemical  decomposition  by  heat  alone;  ELECTROLY- 
SIS is  chemical  decomposition  by  the  galvanic  current.  Both- 
of  these  methods  are  capable  of  a high  degree  of  precision ; 
they  are  also  rapid  and  simple  in  execution. 

8.  The  CHEMICAL  METHODS  proper,  involving  the  use 
of  reagents  and  producing  chemical  transformations  of  the 
given  substance,  may  be  distinguished  as  gasometric,  volu- 
metric and  gravimetric  methods  of  quantitative  analysis. 
The  first  named  is  the  most  recent  and  the  most  rapid,  but 
unfortunately  also  the  most  restricted  in  applicability;  the  last 
named  method  is  the  oldest  and  the  slowest,  but  applicable  in 
all  cases,  and  serves  as  standard  of  comparison  for  the  others. 

9.  In  GASOMETRIC  ANALYSIS,  the  substance  to  be  deter- 
mined is  acted  upon  by  a reagent,  setting  free  some  gas;  this 
gas  is  measured,  and  its  amount  is  proportional  to  that  of 
the  compound  to  be  determined.  It  is  evident,  that  this  reac- 
tion must  be  rapid  and  complete,  and  affect  exclusively  the 
substance  to  be  determined.  Gasometric  analysis  is  entirely 
distinct  from  GAS  ANALYSIS  proper,  which  treats  of  the 
analysis  (by  absorbents)  of  mixtures  of  gases.  Lect.  32. 

10.  In  VOLUMETRIC  ANALYSIS,  the  substance  is  brought 
into  solution,  and  treated  with  some  reagent  of  definite 
strength,  called  a NORMAL  SOLUTION;  this  solution  is  added, 
finally  drop  by  drop,  until  the  reaction  intended  is  completed, 
as  INDICATED  by  some  readily  recognizable  change  in  color 


.218 


LECTURE  45. 


or  appearance.  The  volume  of  normal  solution  used,  then  fur- 
nishes a measure  of  the  strength  of  the  substance. 

11.  In  GRAVIMETRIC  ANALYSIS,  a weighed  portion  of  the 
substance  is,  by  appropriate  reagents,  transformed  into  some 
other  definite  combination,  which  can  be  readily  and  ACCUR- 
ATELY WEIGHED.  The  weight  so  obtained,  furnishes  the 
measure  of  the  strength  sought.  Thus,  a silver  coin  dissolved 
in  nitric  acid,  will  give  all  its  silver  as  precipitate,  when  a 
chloride  is  added;  this  precipitate  washed,  dried,  fused  and 
weighed,  gives  the  weight  of  silver  chloride;  0.7526  thereof  is 
silver,  which  thus  becomes  known. 

12.  Whatever  method  be  used,  in  all  cases  the  real 
determination  depends  on  one  or  more  weighings.  In  volu- 
metric processes,  the  reagents  depend  on  weighings,  and  in  all 
cases  the  substance  taken  must  be  weighed.  Accordingly, 
THE  BALANCE  remains  to-day,  as  it  always  has  been,  THE 
REAL  INSTRUMENT  OF  QUANTITATIVE  CHEMICAL  ANALY- 
SIS, in  all  its  varied  forms  and  under  all  names.  And  in  all  the 
operations  of  quantitative  analysis,  the  chemical  formulm  and 
atomic  weights  are  the  standards  of  comparison.  This  is  the 
legitimate  use  of  chemical  formula. 

46.  THE  ANALYTICAL  BALANCE. 

1.  The  exposition  of  the  general  methods  of  quantitative 
chemical  analysis  must  begin  with  a short  study  of  the  analyti- 
cal balance  (2,  6)  with  AGATE  BEARINGS.  The  handling  of 
this  instrument  is  more  important  than  its  first  cost.  The 
finest  balance  improperly  handled,  can  give  no  reliable  results, 
while  a good  prescription  balance,  in  glass  case,  and  well 
handled,  gives  results  to  2 mgr.  certain,  and  almost  to  the 
single  milligramme. 

2.  In  this  lecture  course  we  shall,  as  a rule,  consider 
weighings  to  the  milligramme  only.  These  can  be  obtained 
by  the  method  of  equal  excursions  of  the  POINTER  (2,  8) 
from  the  central  line  of  the  scale. 


THE  ANALYTICAL  BALANCE. 


219 


In  actual  laboratory  practice,  it  is  advisable  to  determine  the 
scale  value  in  milligrammes;  then  a simple  mental  calculation 
will  give  the  true  milligramme  without  frequent  adjustment 
of  the  pointer. 

3.  The  analytical  balance  is  provided  with  a RIDER  which 
can  be  moved  to  any  division  of  the  scale  marked  on  the  beam, 
while  the  case  is  closed.  Of  course,  the  balance  must  be 
arrested,  as  in  every  case  of  change  of  weights  (2.8).  By 
such  a balance,  even  the  simple  method  of  equal  excursions, 
will  permit  the  determination  of  the  tenth  milligramme. 

4.  The  balance  should  be  PLACED  on  as  firm  and  stable  a 
support  as  can  be  found,  in  good  light,  but  protected  from  the 
direct  rays  of  the  sun.  The  balance  should  be  carefully 
leveled,  by  means  of  a spirit  level  (independent  of  the  unsatis- 
factory box  levels  usually  fastened  to 'the  balance).  All 
necessary  adjustments  should  be  made  and  revised  at  reason- 
able intervals.  Careful  handling  avoids  frequent  change  of 
adjustment. 

5.  A good  balance  should  be  provided  with  a separate  stop 
for  the  pans,  in  addition  to  the  stop  for  the  beam.  Having 
weighed  a burden  on  the  left  pan,  the  balance  should  come  to 
the  same  equilibrium  after  exchanging  the  burden  to  the  right 
and  the  weights  to  the  left  pan ; this  tests  the  EQUALITY  OF 
THE  LEVER  ARMS  (2.6). 

All  trepidations,  all  unnecessary  motions  of  any  kind,  should 
be  avoided,  if  a good  balance  is  to  remain  so.  See  the  instal- 
lation at  Breteuil  (p.  39)  ; the  balances  on  isolated  piers, 
manipulations  by  rods  from  a distance,  and  the  pointer  ob- 
served through  telescopes. 

6.  THE  WEIGHTS,  if  obtained  from  a good  maker,  will 
stand  the  tests  to  a small  fraction  of  a milligramme.  First 
compare  the  tens;  then  one  of  these  with  all  units  (5,  2,  2,  1). 
Next  balance  the  two  tens  against  the  one  twenty.  Finally 
all  these  against  the  fifty.  Like  tests  the  fractional  grammes 
are  subjected  to.  For  all  work  here  considered,  these  tests 
should  be  fully  met  by  the  weights.  For  work  of  higher  pre- 


220 


LECTURE  46. 


cision,  the  actual  errors  are  determined  in  hundredths  of  the 
milligramme  by  the  method  of  oscillation,  not  here  considered. 

7.  All  our  WEIGHINGS  are  made  IN  AIR;  but  air  buoys  up 
all  bodies  to  the  extent  of  the  weight  of  the  air  displaced  by 
the  body  on  the  scale  pans.  This  is  ARCHIMEDES’  principle, 
applied  to  air. 

Now,  a cubic  centimeter  of  air,  under  common  conditions, 
weighs  one  and  one  fifth  milligrammes  (1.2  mgr).  For  a fifty 
gramme  specific  gravity  flask,  this  amounts  to  60  milligrammes 
or  6 centigrammes.-  This  is  evidently  too  much  to  be  over- 
looked. See  3,  12  and  38,  Note. 

8.  Ordinary  weights  are  made  of  turned  brass,  highly 
polished  or  finely  gilt  (2,  7).  The  specific  gravity  or  brass  is 
8.4;  consequently  the  weights  balancing  50  cc  water  occupy 
about  6 cc,  and  therefore  are  buoyed  up  7 mgr. 

If  we  had  actually  50  cc  of  water  on  the  one  pan,  and  50 
gramme  weights  on  the  other,  there  would  be  NO  EQUILI- 
BRIUM. The  water  would  be  buoyed  up  60  mgrs.,  the  weights 
by  7 mgr;  that  is,  equilibrium  would  be  obtained  by  49.947 
grammes,  showing  an  error  of  53  mgr.  for  50  cc  of  water. 

9.  In  all  accurate  work,  this  buoyancy  of  the  air  must  be 
allowed  for.  This  correction  applied  to  the  APPARENT 
WEIGHT  on  the  balance,  gives  the  ABSOLUTE  WEIGHT, 
which  the  body  would  show,  if  weighed  in  vacuo.  Hence  this 
correction  is  also  called  reduction  to  vacuum.  For  every 
gramme,  the  correction  amounts  to  the  number  of  milligrammes 
K given  in  the  following  table,  varying  with  the  specific 
gravity  G of  the  body  weighed.  These  values  are  determined 


as  above. 

Add. 

Add. 

Subtract. 

(} 

K 

G 

K 

G 

K 

0.8 

1.36 

3 

.26 

9 

0.01 

I.O 

1 .06 

4 

.16 

10 

.02 

1.2 

0.86 

.S 

.10 

12 

•05 

1.4 

0.71 

6 

.06 

14 

.06 

1.6 

0.61 

7 

•03 

16 

.07 

1.8 

0.52 

8 

.01 

18 

.08 

2.0 

0.46 

8.5 

.00 

20 

.09 

THE  ANALYTICAL  BALANCE, 


221 


Tlius  32.254  grammes  of  magnesium,  G 1.75  give  K 0.54 
mgr.  per  gramme;  the  correction  therefore  is  17.4  mgr.  and 
the  absolute  weight  32.271  grammes. 

10.  It  is  true  that  this  correction  will  fluctuate  slightly 
with  the  varying  condition  of  the  atmosphere  as  to  tempera- 
ture and  pressure;  but  the  latter  CORRECTION  OF  THE 
CORRECTION  is  an  entirely  insignificant  quantity  and  there- 
fore commonly  disregarded.  Minute  quantities  of  second  order 
are  always  practically  nothing. 

11.  If,  for  analysis,  any  suitable  amount  of  the  substance 
has  been  taken,  it  is  carefully  dried  (in  the  exsiccator,  over 
concentrated  sulphuric  acid)  and  then  weighed  (q).  Now  the 
analytical  operations  are  performed,  the  substance  converted 
into  some  new  compound,  and  this  weighed  (p).  Then  the 
ANALYTICAL  RATIO  a=p/q  has  been  determined ; it  is  the 
weight  of  the  determined  substance  PER  UNIT  of  the  given 
substance.  A number  of  such  determinations  give  a MEAN 
VALUE  representing  the  average  result  of  all  determinations. 

12.  Finally,  this  ratio  is  compared  to  the  ATOMIC  RATIO 
r calculated  from  the  chemical  formula  of  the  two  substances 
(the  one  taken  and  the  one  formed)  with  the  accepted  atomic 
weights.  If  the  analytical  ratio  agrees  with  the  atomic  ratio, 
the  substance  is  proved  pure,  100  per  cent,  strong.  Inversely, 
if  the  substance  had  been  prepared  with  utmost  care,  as  pure 
as  possible,  its  analytical  ratio  agreeing  with  the  atomic  ratio, 
demonstrates  the  correctness  of  the  chemical  formulas  and  the 
atomic  weights  used. 


Note.  For  any  one  series  of  analyses  of  the  same  given  substance, 
determining  the  same  substance  formed  therefrom,  the  analytical  ratio 
must  be  constant;  it  may  fluctuate  slightly,  according  to  the  varying 
imperfections  of  method  and  work,  but  it  should  not  show  any  signs  of 
SYSTEMATIC  VARIATION  with  the  amount  of  substance  taken.  If  it  does, 
such  variation  indicates  a source  of  gravest  error. 

This  is  the  case  with  the  famous  determinations  of  Stas  (see  p.  79). 
Therefore,  his  conclusions  are  without  foundation.  41,  12. 


47.  SPECIFIC  GRAVITY  METHODS. 


1.  The  physical  methods  of  analysis  (45.6)  are  all  very 
useful  and  interesting,  but  we  have  time  for  specific  gravity 
determinations  only  (2,  11,  12).  These  methods  are  both 
practical  and  quite  exact  within  their  proper  sphere.  It 
will  be  easiest  to  first  consider  liquids;  the  methods  may 
thereafter  be  readily  applied  to  solids  also. 

2.  THE  GRADUATED  CYLINDER  weighed  empty  and 
again  when  filled  to  any  mark,  gives  both  weight  and  volume 
of  the  liquid;  hence  its  G.  Weighing  to  the  decigramme, 
estimating  the  volume  to  the  tenth  cc,  it  requires  20  to  40  cc 
to  obtain  results  worth  calculating  to  two  places.'  The  im- 
portance of  the  method  is  its  perfect  clearness.  It  forms  the 
simplest  and  best  introduction  to  specific  gravity  work. 

3.  THE  LITER  FLASK  has  a spherical  form  with  cylindrical, 
narrow  neck,  on  which  is  the  mark.  The  best  flasks  are  pro- 
vided with  ground  glass  stopper;  the  bottom  is  flattened,  the 
glass  thin  and  the  flask  light. 

Weigh  empty  and  filled  to  mark  (3,  5) ; as  the  flask  has  a 
definite  capacity  (10,  25,  50,  100  cc),  all  data  are  known. 
The  first  practice  consists  in  verifying  the  capacity  of  the 
flask  by  using  water,  the  temperature  of  which  should  be 
observed  and  recorded.  Weigh  to  centigramme.  Calculate 
three  decimals. 

4.  THE  PYKNOMETER  or  true  specific  gravity  flask,  is 
usually  provided  with  a ground  glass  stopper  having  a capillary 
perforation.  The  filling  must  be  done  carefully.  Flask  only 
handled  by  points  of  two  fingers,  at  the  neck.  Weigh  to  the 
milligramme;  calculate  G to  four  decimals.  First  use  water 
to  test  the  capacity  of  the  flask,  and  find  the  variations  due 
to  changes  in  temperature.  The  Sprengel  tubes  are  not  re- 
quired for  this  course. 


SPECIFIC  GRAVITY  METHODS. 


223 


').  In  all  these  cases  it  is  essential  that  THE  VESSEL  BE 
CLEAN  AND  DRY  before  filling,  and  diy  on  the  outside  before 
weighing.  The  latter  is  done  by  means  of  soft  filter  paper. 
Working  an  aqueous  solution  exclusively,  washing  with  water, 
followed  by  careful  filming  (3,  3,  Note)  is  sufficient.  If 
changing  to  another  class  of  liquids,  wash,  rinse  with  water, 
rinse  with  alcohol,  film  with  ether  and  dry  by  a current  of 
air  from  a foot  blower.  ' 

6.  The  specific  gravity  of  SOLIDS,  in  fragments,  is  deter- 
mined by  cylinder,  flasks  and  pyknometer,  using  water  if  the 
solid  is  insoluble  therein,  otherwise  some  liquid  (ether,  ben- 
zole), in  which  the  solid  is  insoluble.  Always  take  a relatively 
large  amount  of  solid,  in  comparison  to  the  capacity  of  the 
vessel ; this  secures  higher  accuracy.  Air  bubbles  must  be 
removed;  glass  rod  or  platinum  wire  may  be  used  for  that  pur- 
pose. 

7.  The  solid  having  been  weighed  separately  (w),  also 
the  flask  filled  with  liquid  (a)  and  containing  the  solid  with 
liquid  (b),  we  have  evidently  the  loss  w+a — b as  the  weight 
of  the  liquid  displaced  by  the  solid.  If  the  liquid  be  water, 
then  this  is  the  volume  v,  and  the  specific  gravity  results  by 
the  usual  division.  If  not  water,  the  gravity  g of  the  liquid 
must  be  determined;  divided  into  the  loss,  the  quotient  will 
be  the  volume  v of  the  solid  sought.  Calculate  as  many  dec- 
mals  as  before  directed. 

8.  Any  balance  is  readily  converted  into  our  form  of  HY- 
DROSTIC  BALANCE  by  placing  a crystallizing  dish  on  the 
bench  over  the  left  hand  scale  pan,  suspending  by  a thin 
platinum  wire,  a perforated  platinum  scale  pan  from  the  hook 
into  the  water,  all  adjusted  in  such  a manner  that  when  the 
beam  is  released,  this  submerged  pan  will  be  midway  between 
surface  of  the  water  and  the  bottom  of  the  dish.  On  such  a 
balance,  the  body  is  weighed  first  in  air  (w),  then  in  water 
(a) ; evidently,  w — a is  the  volume  v,  so  that  G can  be  calcu- 
lated. Number  of  decimals  depends  on  the  character  of  the 
balance. 


224 


LECTURE  47. 


9.  No  correction  need  be  applied  on  account  of  the  ex- 
pansion of  the  glass  vessels  used;  for  this  amounts  to  only 
one  forty-thousandth  per  degree.  But  the  EXPANSION  e OF 
THE  WATER  per  unit  is  notable,  as  given  below  in  thousandths 
(or  units  of  third  decimal).  Since  the  standard  is  water  at  its 
greatest  density  (4  degrees),  the  correction  is  the  product 
eG  in  the  third  place,  which  must  be  subtracted  from  G to 
obtain  the  corrected  G'  referring  to  water  at  4 degrees. 

10.  Expansion  e of  one  cubic  centimeter  of  water  in  units 
of  third  place  (thousandths) : 

te  te  te  te 


o 

0.13 

16 

1.03 

30 

4-3 

70 

22.7 

4 

0.00 

20 

1.77 

40 

7-7 

80 

29.0 

8 

0.12 

24 

2.68 

■ 50 

12.0 

90 

CO 

ro 

12 

0.47 

28 

3-79 

60 

17.0 

100 

43-^ 

Reduction  to  vacuum  may  be  necessary  also.  Suppose  the 
division  of  volume  into  weight  had  given  G 10.14-7  for  silver 
at  20  degrees;  then  e 1.77  times  G gives  18  in  third  place, 
hencs  G reduced  to  4 degrees  is  10.129. 

11.  These  methods  are  applied  to  the  determination  of  the 
strength  of  salt  solutions,  commercial  and  pure  acids  and 
alkalies,  sugars,  which  are  heavier  than  water,  also  alcohol 
and  ammonia  which  are  lighter.  The  specific  gravity  found, 
generally  reduced  to  water  at  4 degrees,  is  looked  up  in  the 
tables  of  handbooks  and  the  percentage  of  strength  corre- 
sponding hereto  is  taken  from  the  tables.  A simple  IN- 
TERPOLATION may  be  necessary  to  give  the  exact  value  if 
the  value  of  G is  not  in  the  table.  Heavy  metal  solutions 
should  also  be  used,  such  as  Ka  lo-Hg^te. 

12.  Work  on  solids  is  suitably  connected  with  the  study 
of  important  crystals,  salts,  metals,  minerals  and  ores.  Ordi- 
nary specimens  may  be  used  in  cylinder  and  flasks,  the  finest, 
such  as  gems,  cleavage  pieces,  rarer  metals,  are  excellent  for 
determination  by  the  hydrostatic  balance.  Carried  on  in  this 
manner,  specific  gravity  work  becomes  as  interesting  as  it  is 
practically  useful. 


SPECIFIC  GRAVITY  METHODS. 


Table.  This  short  table  gives  the  number  of  milligrammes 
which  a cubic  centimeter  of  the  following  10  per  cent,  solu- 
tions weighs  in  EXCESS  of  one  gramme: 


Hate 

Clide 

Nate 

Sate 

Cate 

H 

0 

49 

58 

68 

— 

Ka 

92 

65 

64 

(83) 

92 

Na 

111 

72 

67 

92 

105 

Clide: 

Am  30, 

Ca  86, 

Ba  94, 

■Ag  Nate  90 

Sate: 

Mg  105, 

Cu  103, 

Zn  108. 

Pb  Acet.  76 

For  about  5 per  cent,  either  way,  changes  in  G are  pro- 
portional to  amount  dissolved,  and  can  be  calculated  readily. 
Sucrose  40. 

Lighter  than  water  (mgr.  less  than  1 gr.)  are  for  10  per 
cent,  solutions:  Ammonia  42,  alcohol  14. 


48.  ANALYSIS  BY  DISSOCIATION. 

1.  Analysis  by  means  of  the  physical  agencies  (45.7)  and 
without  the  use  of  reagents  proper  or  change  of  vessel,  is 
necessarily  capable  of  a HIGH  DEGREE  OF  PRECISION. 
Thus  Richards,  obtained  in  three  series  of  electrolyses, 
0.25455,  0.25450  and  0.25448  of  metallic  copper  per  unit  of 
blue  vitriol;  the  mean  is  0.25451.  Precisely  the  same  value 
results  by  calculation  from  the  formula  Cu  0^5+5  H2O  for 
Cu  63.5,  confirming  this  value. 

2.  Electrolysis  having  been  considered  sulficiently  (35,  36, 
37),  we  may  devote  this  lesson  mainly  to  DISSOCIATION, 
that  is,  chemical  decomposition  by  means  of  heat.  If  violent 
and  complex  actions  are  avoided,  this  method  of  quantitative 
analysis  can  furnish  very  accurate  results,  there  being  abso- 
lutely no  reagents  used  (hot  even  solvents  as  in  electrolysis 
in  the  wet  way)  and  no  change  of  vessels  is  necessary  during 
the  process. 

3.  Another  important  excellency  of  this  method  we  have  in 
the  fact  that  the  portion  of  matter,  driven  off  by  heat,  can 


22G 


LECTURE  48. 


generally  be  collected  for  qualitative  examination  or  for  weigh-, 
ing.  Thus  the  dissociation  may  be  CHECKED,  both  as  to 
kind  and  amount  of  the  volatile  substance  driven  off. 

4.  It  is,  however,  necessary  that  the  DEGREE  OF  HEAT 
employed  by  reasonably  constant  and  well  selected.  The 
water  bath,  sand  bath  and  air  bath  are  sufficient  to  drive  off 
the  more  volatile  constituents,  such  as  water  and  many  acids. 
A dull  red  heat,  just  making  the  crucible  glow,  or  a bright  red 
heat,  may  be  maintained  by  a Bunsen  Burner,  properly  regu- 
lated. A real  white  heat  requires  the  use  of  blast  or  furnace. 

5.  THE  SUBSTANCE  to  be  analyzed  must  be  pure,  entire- 
ly free  from  volatile  impurities,  such  as  humidity  or  hygro- 
scopic water.  Pulverization  and  drying  over  concentrated 
sulphuric  acid  in  the  exsiccator,  or  in  a current  of  dry  air,  are 
commonly  resorted  to.  Some  crystallized  bodies  lose  WATER 
of  crystallization  by  this  means,  unless  the  temperature  is 
kept  low.  Examination  by  the  microscope  will  show  efflor- 
escence, if  water  is  lost  in  this  way. 

6.  Determinations  of  the  WATER  OF  CRYSTALLIZATION 
are  especially  interesting  and  instructive.  The  sand  or  air 
bath  will  answer;  temperature  about  200  degrees.  Gypsum, 
blue  vitriol,  alum,  borax,  are  a few  of  the  more  common  cases. 
The  formulae  are  Ca  O4S  + 2 HgO;  Cu  O4S  + 5 H2O; 
Ka204S  + Al2  (048)3+24  H2O;  Naa  B04  + 10  H.O; 
they  permit  the  calculation  of  the  amount  of  water  per  unit 
of  weight  (atomic  ratio,  46,  12)  which  will  check  the  amount 
actually  obtained  by  the  determination  (the  analytical  ratio, 
46,  11). 

7.  AT  A RED  HEAT,  in  a platinum  or  porcelain  crucible 
over  a Bunsen  flame,  many  important  analyses  by  dissociation 
are  made.  Blue  vitriol  leaves  copper  oxide,  Cu  O.  Lead 
nitrate  Pb  (03N)2  leaves  lead  oxide  Pb  O (in  porcelain  cru- 
cible). Potassium  bicarbonate,  Ka  H O3C  leaves  the  carbon- 
ate Ka2  O3C;  of  course,  two  atoms  of  the  former  yield  one  of 
the  latter.  Potassium  bitartrate  Ka  H C4H4O6  yields  the 


ANALYSIS  BY  DISSOCIATION. 


227 


carbonate  also.  Crystallized  Am-Mg  phosphate  Mg O4P + 
G H2O  yields  Mg  pyrophosphate,  Mg2  O7  P2  in  all  gravimetric 
phosphate  determinations. 

8.  Dissociations  requiring  a WHITE  HEAT  necessitate  the 
use  of  the  blast  flame  under  the  platinum  crucible.  The  fire- 
clay (Erdmann)  or  graphite  cylinder  around  the  crucible,  facili- 
tates the  work.  Examples  are  common,  results  quite  accurate. 
Calcite  and  any  calcium  carbonate  CaOgC  yields  the  oxide, 
lime,  CaO.  Magnesium  carbonate  yields  the  oxide  already 
at  a red  heat. 

9.  In  all  cases,  the  determination  involves  the  weighing  of 
the  vessel,  taking  substance  and  weighing  the  vessel  with  the 
substance;  igniting,  chilling  on  iron,  cooling  in  exsiccator, 
weighing;  repeating  this  process  TILL  CONSTANT  WEIGHT 
OBTAINED,  that  is,  no  further  loss  sustained  by  renewed 
ignition.  In  all  cases,  the  analytical  ratio  obtained  should  be 
compared  with  the  atomic  ratio  calculated  from  the  formula. 

10.  The  most  useful  technical  analysis  of  coal  is  a process 
of  dissociation,  carefully  worked  out  by  the  author  in  1867  and 
1868  (American  Journal  of  Mining,  New  York,  also  in  German 
and  English  periodicals)  have  become  part  of  general  chemical 
practice.  The  remarkable  increase  in  weight  when  bitumin- 
ous coals  are  dried  for  the  determination  of  moisture,  was  dis- 
covered in  this  research,  and  is  due  to  oxidation  of  the  bitumen 
at  low  temperatures. 


Notes.  The  student  should,  for  practice,  calculate  the  atomic  ratios 
for  the  cases  specified,  and  compare  the  results  with  the  following: 

6.  Gvpsum  0.7907.  Blue  Vitriol  0.6393.  Ka-Alum  0.5443. 

7.  Blue  Vitriol  0.3186.  Lead  Nitrate  0.6254.  Ka  Bicarbonate  0.6900. 
Ka  Bitartrate  0.3670.  Am  Mg  Phosphate  0.4531. 

8.  Ca  Carbonate  0.5600.  Mg  Carbonate  0.4762. 


49.  GASOMETRIC  ANALYSIS. 


1.  Gasometric  Analysis  has  been  DEFINED  (45,  9)  and 
characterized  (45,  5) ; we  have  also  quite  extensively  prac- 
ticed it  (18,  8-11;  24,  7)  and  learned  to  distinguish  it  from 
GAS-ANALYSIS  (32;  33,  3-11;  45,  9).  We  shall  now  briefly 
state  OUR  SPECIAL  METHODS  of  reduction  and  work  in  this 
fascinating  and  admirably  simple  process  of  analysis. 

2.  The  law  of  Avogadro  (40,  10)  asserts  that  the  molecular 
volume  of  all  gasps,  at  the  same  temperature  and  pressure,  is 
the  same.  For  practical  work,  the  milligramme  is  our  unit  of 
weight;  the  mgr.  molecule  of  hydrogen  gas  our  unit  of  volume. 
We  disregard  temperature  and  pressure  by  CHEMICALLY 
DETERMINING  THIS  UNIT  OF  VOLUME  EXPERIMENTALLY, 
i.  e.  the  volume  occupied  by  the  hydrogen  produced  from  24 
mgr.  magnesium. 

3.  This  MGR. MOL. VL.  is  always  nearly  24  cc  at  ordi- 
nary pressures  and  temperatures,  at  which  gasometric  work  is 
done  in  the  laboratory.  That  is,  having  dissolved  an  accur- 
ately (to  tenth  mgr.)  weighed  amount  of  pure  magnesium, 
and  measured  the  gas  volume  produced  in  cc,  the  quotient  of 
the  volume,  divided  by  the  weight,  differs  by  but  a small  frac- 
tion from  unity;  say  by  e per  cent.  Then  all  volumes  ob- 
served in  analysis,  at  the  time,  must  be  reduced  that  number 
of  per  cent.,  to  bring  the  volume  to  our  standard. 

4.  Our  ordinary  GAS  BURETTE  is  the  simplest  possible, 
readily  made  from  any  Mohr’s  burette  and  a pipette,  as  shown 
in  our  plate  of  Apparatus.  We  also  make  use  of  the  Hempel 
gas  burette  with  perforated  stop  cock,  (3,  10,  11)  but  in 
reversed  position,  and  provided  with  pipette-reservoir;  we 
use  this  both  with  water  and  mercury.  A simple  water- 
jacket,  consisting  of  a glass  tube  surrounding  the  burette  and 
exceeding  it  about  6 m m in  width,  filled  with  water,  suffices. 
A thermometer  is  inserted  in  the  pipette -bulb  receiver. 


GASOMETRiC  ANALYSIS. 


229 


5.  OUR  EVOLUTION  VESSELS  vary  considerably,  accord- 
ing to  the  object  for  which  they  are  used.  The  simplest  is  an 
ordinary  test  tube,  fastened  by  means  of  a cork  in  a cylindri- 
cal stand  glass  but  little  wider,  the  space  being  filled  with 
water,  while  the  test  tube,  by  means  of  perforated  stopper, 
allows  connection  with  the  burette  by  rubber  tube  of  small 
bore. 

We  work  the  evolution  at  all  temperatures,  the  only  condi- 
tion being  that  the  temperature  is  the  same  at  the  final  and  at 
the  initial  reading  of  the  burette. 

6.  When  necessary  we  insert  between  the  evolution  vessel 
and  the  burette  our  AIR  LOCK,  simply  a U-tube  of  proper 
capacity  (100  or  200  cc)  having  enough  lead  foil  wrapped 
around  one  branch  to  stay  down  in  a tall  beaker  with  water; 
by  judicious  use  of  black  paint,  the  lead  sticks  to  the  glass 
and  does  not  corrode.  At  the  close  of  each  determination, 
after  detaching  the  evolution  vessel,  a few  motions  of  the  reser- 
voir thoroughly  ventilate  the  air  lock,  filling  it  with  atmospheric 
air.  The  principle  here  used  is  that  of  displacement. 

7.  Gases  acting  upon  air  are  handled  IN  ANY  SUITABLE 
GAS;  thus  nitric  oxide  in  hydrogen.  In  such  experiments  the 
Hempel  burette  is  most  serviceable,  on  account  of  that  per- 
forated stop  cock.  A Kipp  and  the  necessary  washing  flasks 
are  connected  with  the  evolution  vessel,  by  means  of  a tube 
with  stop  cock. 

The  determinations  being  very  rapid,  hydrogen  does  not 
leak  appreciably;  but  using  an  air  lock  connected  by  glass 
tubing,  even  this  error  may  be  overcome  entirely. 

8.  Under  these  conditions,  the  reduced  gas  (3  and  4 above) 
weighs  per  cubic  centimeter  as  many  milligrammes  as  its 
molecular  weight  divided  by  24.  That  is,  a cubic  centimeter 
of  the  following  gases,  after  such  reduction,  weighs  the  num- 
ber of  milligrammes  stated:  H,  0.083  (iV)  ; N,  1.1G6  (IJ); 
O,  1.333  di) ; Cl,  2.958  (2|i) ; NO,  1.250  (1|)  ; CO.,  1.833 
(Ij).  UreaCH40N2,  2.500  (21).  Sweet  spirits  of  nitre, 
3.125  (3i). 


230 


LECTURE  49. 


For  solubility  allow  a volume  equal  to  that  of  the  liquid 
used  in  the  case  of  NO  and  CO 2. 

9.  As  to  PROCESSES  employed,  hydrogen  is  produced  by 
acids  and  magnesium;  carbon  dioxide  by  acids  and  most  car- 
bonates; nitrogen  from  urea  and  a strong,  fresh  solution  of 
hypobromite;  chlorine  from  hypochlorites  or  chlorine  water 
and  peroxide  of  hydrogen;  oxygen  from  permanganate  and 
peroxide  of  hydrogen ; nitric  oxide  from  sweet  spirits  of  nitre, 
Ka  lo’^^e  and  H in  an  atmosphere  of  hydrogen.  The  sub- 
stance used  as  reagent  must  be  in  excess;  in  the  last  example, 
there  must  be  an  excess  of  permanganate  if  the  peroxide  is  to 
be  determined,  while  if  permanganate  is  to  be  determined,  an 
excess  of  peroxide  must  be  taken. 

10.  The  QUANTITATIVE  RELATION  between  the  VOLUME 
of  the  gas  produced  and  the  WEIGHT  of  the  substance  taken 
must  be  carefully  established  before  the  process  can  be  accep- 
ted. The  reaction  must  also  be  quick  and  complete. 

For  hydrogen,  we  obtain  one  equivalent  for  each  equivalent 
of  metal  dissolved.  But  this  process,  being  fundamental,  we 
use  to  determine  the  unit  or  equivalent  volume  of  hydrogen 
itself,  to  make  us  independent  of  variations  in  temperature 
and  pressure. 

11.  Carbonates  give  one  molecule  of  fixed  air  for  each 
double  equivalent.  Consequently,  100  mgr.  Ka  Bicarbonate 
rnust  yield  24  cc  gas;  or  every  cc  gas  represents  4.16  mgr.  of 
the  true  bicarbonate.  Thus  the  percentage  of  pure  bicarbon- 
ate in  the  sample  taken  becomes  known.  In  the  same  way, 
each  cc  nitrogen  gas  representing  2.5  mgr.  of  urea,  the  gas 
evolved  from  a measured  quantity  of  urine  gives  its  per  cent, 
of  urea.  Hypochlorites  give  a volume  of  oxygen  gas  exactly 
equal  to  that  of  the  effective  chlorine;  or  2 Ca  OCl=183 
yield  one  molecule  O,  hence  every  cc  gas  corresponds  to  7.625 
Ca  hypochlorite. 

12.  It  will  readily  be  seen  that  this  method  of  analysis  has 
received  a considerable  extension  at  our  hands.  Further 
details  will  be  given  in  the  laboratory  course. 


GASOMETRIC  ANALYSIS. 


231 


As  to  CALCULATIONS,  one  example  will  suffice.  Suppose 
42.7  mgr.  Mg  gave  44.5  cc  gas;  hence  1 mgr.  gave  1.042  cc; 
reduction  4.2  per  cent. 

Peroxide  of  hydrogen,  mixed  with  an  equal  volume  of  dilute 
sulphuric  acid;  5 cc  mixture  gave,  with  excess  of  permanga- 
nate, 57.2  cc  gas.  The  4.2  per  cent,  is  2.4  cc,  leaving  54.8 
cc  reduced;  hence  10.96  vols. ; weight  one  and  a third  gives 
14.61  mgr.  oxygen  per  cc  peroxide,  or  1.46  per  cent,  by  weight 
of  oxygen;  or  3.1  per  cent,  peroxide,  by  weight. 


Note.  A cubic  centimeter  of  dry  air  weighs  1.2  mgr.  at  the  following 
temperatures  and  pressure  (mm)  : 

t I 5 9 13  17  21  25  29 

p 710  720  730  740  750  760  770  7S0 

The  CHANGE  in  weight  amounts  to  one  per  cent,  for  3 degrees  in  tem- 
perature and  for  7 millimeters  pressure. 

By  this  simple  table  of  reduction,  the  weight  may  be  calculated  from 
the  observed  pressure  and  temperature.  For  example,  at  18  degrees  and 
735  mm,  we  calculate  from  nearest  17  degrees  750,  as  follows:  i degree 
high,  weight  P®’''  cent,  low;  15  mm  low,  weight  2 per  cent,  low;  total 
2^3  per  cent,  lovv,  on  1.2  mgr.  is  0.028  low,  say  0.03:  hence  weight  of  one 
cc  air  at  18  degrees  and  735  mm  is  1.17  mgr. 

Same  correction  per  cent,  must  be  applied  to  weights  given  in  8 if  this 
mode  of  reduction  by  barometer  and  thermometer  reading  be  preferred. 

In  this  mode  of  reduction,  it  must  be  remembered  that  the  vapor  pre's- 
sure  must  be  subtracted  from  the  reduced  barometer  reading  to  get  the 
pressure  of  the  dry  gas  required.  This  vapor  pressure  is,  in  mm  mer- 
cury : 

temp.  6 10  14  18  22  26  30 

vap.  press.  7.0  9.1  11.9  15.4  19.7  25.0  31.6 

For  chemical  purposes,  the  reduction  given  in  the  text  is  both  easiest 
applied  and  most  rational. 


50.  VOLUMETRIC  ANALYSIS. 

1.  This  excellent  method  of  quantitative  analysis  has  been 
exemplified  in  lecture  24  for  the  measurement  of  acids  and 
bases.  A general  definition  thereof  has  also  been  given 
(45.10).  This  method  of  analysis  was  founded  by  GAY- 


232 


LECTURE  50. 


LUSSAC  (1824  to  1832)  and  was  brought  into  system  by 
MOHR  (Titrir-Methode,  1855).  We  will  now  present  the^ 
leading  principles  and  modes  of  practice  of  the  same. 

2.  The  two  kinds  of  TEST  SOLUTIONS  introduced  by  these 
chemists  continue  in  use — each  being  most  convenient  in  its 
own  sphere.  When  many  determinations  of  the  same  kind 
have  to  be  made,  the  Gay-Lussac  STANDARD  SOLUTION, 
representing  a centigramme  or  milligramme  of  the  substance 
per  cubic  centimeter,  is  used.  If  a greater  variety  of  work  has 
to  be  done  by  the  least  number  of  test  solutions,  the  NORMAL 
SOLUTIONS  of  Mohr  are  the  most  practical. 

3.  Silver,  Ag=108  is  precipitated  by  salt,  Na  Cl=58.5; 
accordingly  the  atomic  ratio  of  silver  to  salt  is  1 : 0.5417.  A 
cubic  centimeter  of  salt  solution  will  therefore  precipitate  one 
milligramme  of  silver,  if  it  contains  0.5417  mgr.  salt  per  cc,  or 
0.5417  grammes  per  liter.  A cubic  centimeter  of  salt- solution 
will  precipitate  a centigramme  of  silver,  if  it  contains  5.417 
grammes  of  salt  per  liter.  Such  solutions  are  standard  solu- 
tions according  to  GAY-LUSSAC;  the  number  of  cubic  centi- 
meters used  directly  gives  the  weight  of  the  silver  or  substance 
sought. 

4.  The  normal  solutions  of  MOHR  contain  a milligramme - 
equivalent  per  cubic  centimeter  (24.6  and  45.10).  A normal 
salt  solution  therefore  is  made  by  dissolving  58.5  grammes  of 
pure  sodium  chloride  to  a liter;  and  each  cubic  centimeter 
thereof  will  precipitate  one  milligramme-equivalent  of  silver, 
that  is  108  mgrs.  A tenth -normal  salt  solution  is  made  dis- 
solving 5.85  gr.  salt  to  a liter,  and  each  cc  thereof  precipitates 
10.8  mgr.  silver. 

5.  The  Mohr  solutions  can  also  be  used  to  determine  the 
PER  CENT.  STRENGTH  of  any  given  substance,  without 
calculation,  by  WEIGHING  OFF  A PROPER  QUANTITY,  de- 
termined by  the  equivalent  weights.  Thus  if  each  cc  of  the 
tenth  normal  solution  is  to  represent  one  per  cent.,  the  total 
100  per  cent,  silver  must  equal  100  cc  tenth  normal  or  10 


VOLUMETRIC  ANALYSIS. 


233 


normal  = 10  times  108  mgr.  = 1.080  grammes  of  silver.  If 
this  amount  of  silver  (alloy)  is  dissolved,  it  will  require  as 
many  cc  tenth  normal  salt  solution  as  it  contains  per  cent,  of 
pure  silver.  In  general,  take  100  mgr.  equiv.  and  1 per  cent, 
will  be  precipitated  by  1 cc  N solution. 

6.  We  have  now  presented  really  all  principles  required  in 
the  calculation  of  volumetric  work.  Suppose  the  strength  of 
aqua  ammonia  were  to  be  determined  by  normal  acid  in  per 
cent,  of  ammonia  gas,  NH3  = 17.  Then  100  cc  normal  would 
contain  1700  mgr.  NH3  = 1.7  gramme.  Take  1.7  grammes  of 
the  aqua  ammonia,  and  neutralize  with  normal  acid;  the  num- 
ber of  cc  used  evidently  are  the  per  cent.  NH3  gas  in  the 
liquid.  If  half  the  quantity  be  taken,  every  cc  normal  acid 
represents  2 per  cent. 

7.  Of  the  principal  lines  of  volumetric  work,  NEUTRALI- 
ZATION has  already  been  considered  (Lect.  24).  In  practice, 
each  cc  of  normal  acid  measures  an  equivalent  amount  of 
alkali ; that  is,  one  mgr.  equiv.  In  numbers,  17  mgr.  ammonia ; 
40  mgr.  NaHate  (NaOH);  56  mgr.  Ka  Hate  (KaOH).  In  the 
same  way,  each  cc  normal  alkali  measures  one  mgr.  equiv.  of 
any  acid.  In  numbers,  63  mgr.  nitric  (HO3N)  ; 49  mgr.  sul- 
phuric 4(H204S). 


8.  THE  CHAMELEON  PROCESS  has  been  considered  so 
far  as  to  show  that  every  2 atoms  of  the  reagent  (Ka  O4  Mn, 
= 158)  set  free  5 atoms  of  oxygen  (10  equivalents) ; or  1 mgr. 
equivalent  oxygen  corresponds  to  31.6  mgr.  of  pure  permanga- 
nate. Tenth -normal  requires  3.16  gr.  per  liter. 

The  standardizing  is  done  with  the  pure,  crystallized 
hydrated  ammonio-ferrous  sulphate,  Am204  S + Fe04S  -|- 
6 H2O  = 392  (see  15,  11).  Two  of  this  salt  require  one  atom 
of  oxygen  (see  44.9)  hence  39.2  is  tenth -normal.  In  the 
presence  of  a large  .excess  of  sulphuric  acid,  the  reaction  is 
quick  and  sharp.  Add  permanganate  to  acid  ferrous  solution 
till  color  no  longer  disappears.  The  so-called  “florist’s  wire” 
generalfy  used  for  standardizing,  is  not  pure  iron. 


234 


LECTURE  51. 


9.  THE  IODINE  PROCESS,  due  to  Bunsen  (p.  24)  is  typi- 
fied in  the  reaction  between  the  HYPO  and  the  iodine  solution; 
using  a trifle  of  starch  paste  as  indicated  (BLUE  with  smallest 
trace  of  FREE  iodine,  23,  4).  Pure,  crystallized  Na  Hyposul- 
phite is  represented  by  NasOgSa+S  HgO  = 248.  Two  of  this 
THIOSULPHATE  react  with  two  iodine,  giving  two  Na  lo  and 
the  so-called  tetrathionate  NaaOeSi;  hence  248  hypo  corre- 
spond to  127  iodine.  Tenth -normal  hypo  must  contain  24.8 
mgr.  per  cc,  and  is  equivalent  to  12.7  iodine,  or  8.0  bromine, 
or  3.55  chlorine.  The  iodine  is  kept  in  solution  by  an  excess 
of  Ka  loide — best  twice  the  weight  of  the  iodine.  Twentieth 
normal  is  more  convenient  for  use. 

10.  PRECIPITATION  of  neutral  chloride  by  silver  permits 

the  use  of  Ka  Cr^te  as  indicator;  when  all  precipitated 

as  Ag  the  next  drop  will  show  the  red  color  due  to 

Ag  Crate  (Mohr). 

A tenth -normal  Ag  Nate  solution  is  obtained  by  dissolving 
17  grammes  of  the  nitrate  (Ag  O3N  = 170)  to  the  liter.  Every 
cc  hereof  will  represent  the  following  equivalents:  5.85  mgr. 
Na  Cl;  15.0  mgr.  Na  lo;  7.45  mgr.  Ka  Cl;  16.6  mgr.  Ka  lo; 
8.7  mgr.  Li  Br;  15.5  mgr.  Fe  loa.  These  data  are  easily 
calculated  from  the  formulas  given. 


51.  GRAVIMETRIC  ANALYSIS. 

1.  In  gravimetric  analysis,  a weighed  amount  of  the  sub- 
stance is  chemically  changed  to  some  well-defined  compound, 
sufficiently  permanent  to  permit  accurate  weighing.  The 
chemical  formula  of  this  compound  will  tell  how  much  it  con- 
tains of  the  ingredient  to  be  determined.  Thus  the  amount 
in  a UNIT  OF  WEIGHT  of  the  original  substance  becomes 
known.  See  45,  11 . 

2.  Suppose  that  the  amount  of  CALCIUM  in  a given  sub- 
stance were  to  be  determined.  The  weighed  substance 
is  dissolved  in  acid,  filtered;  heavy  metals  removed,  if 


GRAVIMETRIC  ANALYSIS. 


235 


present;  filtrate  made  ammonical  and  the  calcium  precipitated 
as  oxalate,  that  being  the  most  insoluble  d'alcium  compound. 
Filter,  wash,  dry  on  water  bath,  weigh  the  crystallized  oxalate, 
Ca  O4C2  + H2O  = 146.  In  platinum  crucible,  at  dull  red- 
ness, it  changes  to  carbonate,  Ca  OsC^  100,  which  weigh. 
Ignite  with  blast  at  white  heat;  it  becomes  the  oxide  (or  lime) 
Ca  O = 56,  which  weigh. 

8.  From  the  formula  given  it  is  easy  to  CALCULATE  that 
a unit  of  weight  of  crystallized  oxalate  represents  0.2740  of 
Ca,  the  carbonate  0.4000  and  the  oxide  0.7143  of  Ca.  In  a 
like  manner  the  oxalate  represents  0.3836  of  oxide  and  the 
carbonate  0.5600  thereof.  If  then,  any  of  these  compounds 
found  had  been  weighed,  the  corresponding  amounts  of  Ca  or 
of  Ca  O is  readily  calculated  by  the  values  just  given.  In 
this  way  the  percentage  in  the  original  substance  becomes 
known. 

4.  Now,  which  of  these  compounds  gives  the  MOST  AC- 
CURATE RESULTS.^  Not  the  oxalate,  for  it  is  difficult  to  avoid 
a loss  of  water  of  crystallization  in  drying  the  precipitate;  not 
the  carbonate,  for  overheating  reduces  it  to  oxide,  insufficient 
ignition  may  leave  some  oxalate.  Evidently,  the  oxide,  ob- 
tained last  is  the  best  compound  to  use,  for  it  need  only  be 
ignited  till  constant  weight,  since  it  is  not  volatile  at  all. 

5.  We  have  already  shown  that  SILVER  is  weighed  as 
CHLORIDE  (45,  11).  It  need  hardly  be  added,  that  chlorides 
are  determined  in  the  same  way,  by  the  same  compound,  upon 
adding  an  excess  of  silver  solution. 

The  calculations  are  based  upon  the  formula  Ag  Cl=143.5. 
Every  143.5  Ag  Cf^®  weighed  represent  108  silver  in  the 
original ; or  the  weight  of  Ag  Cn^®  found,  multiplied  by  0.7525, 
will  give  the  weight  of  the  silver. 

6.  In  the  same  manner  the  exceedingly  insoluble  Ba 

is  formed  and  weighed  for  the  determination  of  the  amount  of 
sulphate— by  adding  Ba  solution;  and  for  the  determination  of 
barium— by  adding  a soluble  sulphate.  To  obtain  accurate 


236 


LECTURE  51. 


results,  the  MINUTl.^  of  the  operation  must  be  studied  and 
practiced;  precipitation,  washing,  igniting,  in  fact,  every 
operation  has  to  be  as  nearly  perfect  as  possible  in  order  to 
obtain  reliable  results. 

7.  Another  compound  of  great  importance  in  gravimetric 
analysis,  is  the  crystallized  hydrated  ammonio- magnesium 
phosphate,  almost  absolutely  insoluble  in  ammoniacal  (CHde 
and  Hate)  solutions.  After  filtering  and  washing  it  is  dried, 
ignited  and  weighed  as  magnesium  pyrophosphate  (48.7). 
The  Mg2  O7  P2=222  represents  Pg  05=141  of  the  so-called 
anhydrous  phosphoric  acid  and  80  of  Mg  O.  That  is,  0.6351 
thereof  is  P2  O5  and  0.3603  is  magnesia,  either  of  which  is 
so  determined. 

8.  The  metals  may  often  be  determined  as  oxide.  Thus 
iron  compounds  are  generally  determined  as  ferric  oxideFea  O3 
=160.  Ferric  salts  are  directly  precipitated  by  ammonia, 
filtered,  washed,  ignited  and  weighed;  ferrous  are  readily 
oxidized  with  nitric  acid  to  ferric,  and  treated  as  just  stated. 
Since  Fe  0=72,  160  ferric  oxide  correspond  to  144  ferrous 
oxide  and  to  112  iron.  By  these  numbers  the  reductions 
necessary  can  be  made. 

9.  Platinum  chloride  gives  a crystallized  precipitate  of  Am 
CIO  ptate  ^ith  sal-ammoniac,  especially  when  alcohol  present. 
This  salt,  Amg  Cle  Pt=443  represents  36  ammonium  and  194 
platinum;  ignited,  it  leaves  only  the  latter,  which  thus  repre- 
sents 36  ammonium  or  34  ammonia  gas.  This  is  only  0.0767 
of  the  crystallized  salt,  thus  may  serve  for  accurate  determi- 
nations. 

10.  The  subject  of  quantitative  analysis  is  as  difficult  as  it 
is  important.  While  only  laboratory  work  will  make  these 
processes  thoroughly  understood  and  familiar,  it  is  hoped  that 
these  carefully  selected  examples  will  suffice  to  make  the  stu- 
dent comprehend  the  methods  employed  and  the  value  of  the 
results  obtained.  While  an  application  of  chemical  formulas, 
quantitative  analysis  really  is  equally  demonstrating  the  truth 
of  the  chemical  formulas  themselves. 


52.  SPECTRUM  ANALYSIS. 


1.  The  rainbow  shows  a SPECTRUM  of  sun  light.  Look- 
ing through  a prism  at  any  narrow  band  of  white,  we  see  a 
corresponding  series  of  colors.  The  least  deflected  from  the 
straight  line  of  sight,  is  the  red;  then  comes  orange,  yellow, 
green,  blue,  indigo  and  violet,  which  is  the  most  deflected. 
Newton  (1671)  first  thoroughly  studied  the  solar  spectrum 
obtained  through  glass  prisms. 

2.  In  these  spectra  the  colors  blend  and  overlap.  Narrow- 
ing the  band  of  light — by  means  of  an  adjustable  slit  in  the 
shutter  of  a darkened  room — the  colors  become  more  distinct 
and  pure,  but  at  the  same  time,  the  total  intensity  becomes 
less.  By  observing  through  a telescope,  more  light  enters  the 
eye,  the  pupil  of  which  is  thereby  virtually  enlarged  to  the 
size  of  the  object  glass  of  the  telescope.  This  was  first  done 
by  Fraunhofer  of  Munich  (1814).  He  obtained  the  best  de- 
fined spectrum  of  the  sun,  the  purest  and  most  brilliant.  But 
he  was  surprised  to  find  many  parts  of  the  spectrum  missing — 
replaced  by  fine  black  lines,  the  so-called  FRAUNHOFER 
LINES  of  the  spectrum.  He  counted  thousands.  The  most 
notable  he  designated  by  the  letters  of  the  alphabet  from  A to 
H ; groups  of  lines  he  marked  a,  b.  See  upper  spectrum,  p.  72. 

3.  For  greater  convenience,  Kirchhoff  (p.  35)  and  Bunsen 
(p.  24)  combined  all  these  pieces  of  apparatus  on  one  frame, 
and  called  the  instrument  resulting,  a SPECTROSCOPE  (1860). 
For  ordinary  chemical  work,  the  DIRECT  VISION  spectroscope 
is  the  most  convenient.  It  has  the  narrow,  adjustable  SLIT 
turned  towards  the  light.  Then  comes  a powerful  SYSTEM 
OF  PRISMS  (of  3 crown  and  2 flint  glass  prisms) ; finally  a 
small  telescope.  All  these  parts  are  enclosed  in  one  tube. 

4.  Looking  through  such  a spectroscope  at  the  sky,  first 
narrow  the  slit  till  almost  shut,  then  slide  the  telescope  in  or 
out  till  distinct  vision  of  the  Fraunhofer  lines.  The  black  line 


238 


LECTURE  52. 


D in  the  yellow,  and  the  line  E in  the  green  near  the  group  b 
will  be  readily  recognized.  The  instrument  is  now  ADJUSTED 
for  chemical  work. — It  is  best  to  revolve  the  spectroscope  till 
the  spectrum  appears  horizontal  with  the  red  to  the  left,  as 
they  are  conventionally  represented  in  spectrum  plates  (p.  72) . 

5.  Looking  at  the  colorless  flame  of  a Bunsen  Burner,  it 
will  be  almost  invisible;  a yellow  line  may  flash  up  from  time 
to  time,  due  to  traces  of  sodium  almost  everywhere.  Intro- 
ducing a clean  (ignited  till  imparting  no  color  to  flame)  plati- 
num loop  that  has  touched  a sodium  compound  or  solution,  a 
brilliantly  luminous  line  will  flash  up  in  the  yellow.  If  the 
Bunsen  flame  is  so  placed  that  good  daylight  can  enter  the 
spectroscope  through  the  flame,  the  solar  and  the  sodium 
spectrum  will  be  seen  simultaneously.  The  yellow  sodium 
line  is  then  seen  to  coincide  with  the  line  D.  There  is  sodium 
in  the  sun. 

6.  The  spectra  of  the  elements  which  can  be  observed  in 
this  manner,  using  the  heat  of  the  Bunsen  flame  only,  are 
mapped  on  page  72.  The  most  characteristic  bright  lines  are: 
extreme  red  for  Ka;  brilliant  red  (near  C)  Li;  blue  line 
(beyond  F),  Sr;  brilliant  orange,  yellow  and  green  line,  Ca; 
group  of  3 or  4 bright  green  lines,  Ba.  By  the  two  lines  in 
the  violet,  Bunsen  recognized  the  NEW  ELEMENT  rubidium 
(Rb).  By  the  two  lines  in  the  blue,  he  found  caesium  (Cs). 
The  extremely  bright,  but  very  transitory  line  in  the  green, 
revealed  Thaltium  (Tl)  to  Crooks  of  England  and  Lamy  of 
France. 

7.  By  means  of  the  electric  sparks  of  a Ruhmkorff  coil,  the 
heavy  metals  are  volatized  in  minimal  quantities,  but  sufficient 
to  show  their  spectra  brilliantly.  These  spectra  are  too  com- 
plex, consist  of  too  many  lines,  to  be  useful  in  ordinary  chemi- 
cal practice. 

The  discharge  of  the  coil  through  rarified  gases  (in  Pluecker 
tubes,  contracted  in  the  middle)  gives  fine  line  spectra  for 
ready  chemical  identification.  The  hydrogen  spectrum  con- 
sists of  a red  and  a blue  line,  coinciding  with  the  Fraun- 


SPECTRUM  ANALYSIS. 


2:^9 


hofer  C,  F and  a violet  line  near  G.  By  its  spectrum,  argon 
is  distinguished  from  nitrogen  (38,  10). 

8.  At  lectures,  before  the  general  public,  many  of  these 
phenomena  are  projected  on  the  screen.  For  scientific  stu- 
dents it  is  preferrable  to  show  these  phenomena  individually 
at  an  EXHIBITION,  where  the  different  instruments  are  in 
charge  of  one  or  two  students  each,  who,  by  their  advanced 
work  in  the  laboratory,  have  bocome  familiar  therewith.  This 
is  the  only  way  to  show  the  flame  and  gas  spectra  in  their 
real  beauty. 

9.  Twenty  years  ago,  a line  in  the  spectrum  of  the  solar 
corona  was  discovered,  on  the  absolute  or  wave  length  scale 
at  Dg  =587.5,  near  the  Na  line,  which  shows  double  in  such 
powerful  instruments,  at  02=588.9,  and  Di=589.5.  No  ter- 
restrial element  showing  that  line,  it  was  ascribed  to  some 
hypothetic  element  peculiar  to  the  solar  corona,  and  named 
Helium. 

10.  When  Lord  Rayleigh  had  discovered  argon  in  the  air. 
Professor  Ramsey,  searching  for  mineral  sources  of  argon,  found 
a gas,  giving  the  characteristic  Dg  line,  on  treating  Cleveit 
with  sulphuric  acid  (1895).  This  gas  is  that  substance 
of  the  solar  corona  called  Helium.  Its  density  is  twice  that  of 
hydrogen,  its  atomic  weight  is  taken  at  4.  Like  argon,  it  is 
nullovalent,  does  not  combine  chemically.  One  gramme  of 
cleveit  (a  rare  Uranium  mineral)  gives  about  7 cc  helium  gas. 
It  has  also  been  found  in  rare  Yttrium  minerals  (Fergusonite, 
Samarskite) . 

11.  If  a direct  vision  spectroscope  be  substituted  for  the 
eye  piece  of  a telescope,  the  spectra  of  the  stars  and  nebulae 
can  be  observed,  as  well  as  the  spectrum  of  any  part  of  the 
sun,  its, spots,  protuberances  and  other  details.  Huggins, 
Janssen,  Lockyer  and  others  have  developed  this  part  of 
astronomy  which  may  be  considered  as  COSMICAL  CHEMIS- 
TRY. Father  SECCHI  (p.  29)  has  labored  most  successfully 
in  this  field,  and  first  classified  the  stars  according  to  their 


240 


LECTURE  53. 


spectra,  i.  e.  their  chemical  composition.  The  telescope  of 
Galilei  showed  the  form  (p.  44)  while  the  spectroscope  reveals 
the  chemical  nature  of  the  stars. 

12.  When  tne  spectroscope  is  directly  against  the  bright 
sky  so  as  to  show  the  solar  spectrum  well,  a test  tube,  con- 
taining a dilute  solution  of  any  coloring  material,  held  before 
the  slit,  will  blot  out  parts  of  the  spectrum,  sometimes  show- 
ing definite  black  lines.  These  spectra  are  called  ABSORP- 
TION SPECTRA.  The  spectra  of  chlorophyll,  red  blood 
(arterial)  and  blue  blood  (veinous)  are  quite  characteristic. 
These  absorption  spectra  are  most  useful  to  organic  chemistry. 


53.  DRY  WAY  ANALYSIS. 

1.  After  having  shown  how  the  chemical  formulae  of  com- 
pounds are  established  and  applied  for  quantitative  determina- 
tions, we  will  complete  the  introduction  to  the  inorganic  part 
of  chemistry  by  a systematic  exposition  of  the  principal 
QUALITATIVE  TESTS,  both  in  the  dry  and  the  wet  way. 
This  course  we  have  found  much  more  interesting  and  useful 
than  a synopsis  of  systematic  chemistry. 

2.  The  chemical  blowpipe  has  been  described  (Lect.  5) 
and  its  use  has  been  frequently  required  (Lectures  5,  6,  7,  9, 
10,  11,  18,  26).  We  have  learned  to  appreciate  the  blowpipe 
reactions  (PYROGNOSTICS)  because  they  require  but  a small 
instrument  and  a few  of  the  simplest  reagents,  while  giving 
definite  results  quickly  and  with  but  little  labor — provided 
some  skill  has  been  acquired.  All  the  typical  tests  can 
be  well  shown  at  lectures,  so  that  even  those  who  do  not 
practice  themselves  will  quite  well  understand  the  subject. 

3.  THE  FIRST  TEST  is  made  by  heating  a minute  sample 
on  charcoal.  The  general  results  to  be  looked  for  are:  1,  com- 
plete VOLATILIZATION,  with  or  without  odor;  2,  a RESIDUE 
(i.  e.  where  the  substance  was  placed),  and  noting  whether 
this  residue  is  WHITE  or  NOT  WHITE,  also  whether  it  pro- 


DRY  WAY  ANALYSIS. 


241 


duces  FLAME  COLORATION.  Next  look  for  an  INCRUSTA- 
TION, i.  e.  deposit  forming  at  some  distance  from  the  sample; 
and  lastly,  look  for  a REGULUS.  Compare  diagram,  p.  73 
(dry  way) . 

4.  If  the  substance  volatilizes  completely,  repeat  the  ex- 
periment and  examine  carefully  whether  an  ODOR  can  be 
recognized;  that  of  burning  sulphur  proves  S;  of  garlic,  some 
As  compound.  If  no  odor,  heat  the  substance  with  lime  in  a 
blowpipe  glass  tube;  a distillate  of  white,  metallic  globules 
proves  an  Hg  compound;  odor  of  ammonia,  an  ammonium 
compound. 

5.  If  the  RESIDUE  IS  WHITE,  it  may  show  a)  FLAME 
COLORATION  or  simply  be  an  incandescent  b)  INFUSIBLE 
mass.  In  the  first  place  (a)  repeat  the  test  on  the  platinum 
loop:  flame  yellow,  Na;  yellowish-green,  Ba;  orange,  Ca; 
crimson,  Sr;  violet-purplish,  Ka.  Of  these  flames,  Na,  Ba, 
Ca  are  invisible  through  blue  glass,  through  which  Ka,  Sr 
show  finely;  while  these  are  invisible  through  a green  glass 
which  shows  Na,  Ba,  Ca  well.  In  (b)  ignite  after  adding  a 
drop  of  Co  solution;  color  pale  rose.  Mg;  green,  Zn;  blue, 
A1  (see  7,  9). 

G.  If  an  INCRUSTATION  has  formed,  note  its  color,  size, 
and  see  whether  there  is  also  a regulus.  Incrustation  WHITE; 
very  large,  odor  of  garlic.  As;  smaller,  nearer  sample,  with 
brittle  regulus,  smoking,  Sb;  white  when  cold,  yellow  while 
hot,  Zn  (try  Co  solution)  ; YELLOW  with  brittle  regulus,  Bi, 
with  malleable  soft  regulus,  Pb;  YELLOWISH,  close  to  sample, 
regulus  difficult  except  with  cyanide  flux,  Sn;  BROWN,  no 
regulus,  Cd;  pale  red,  very  light  in  amount,  with  fine  white 
globular  regulus,  Ag. 

7.  A REGULUS  WITHOUT  INCRUSTATION  may  appear  as 
GLOBULE  (Cu,  Ag,  Au,  see  7,  1-3)  or  as  SPANGLES.  In  the 
latter  case,  the  metal  is  generally  not  visible,  except  after 
cutting  out  the  charcoal,  grinding  it  under  water  in  an  agate 
mortar,  and  washing  the  light  carbon  particles  off;  the  heavy, 
metallic,  now  partly  flattened  grains  and  spangles,  will  remain 


242 


LECTURE  53. 


at  the  bottom  of  the  mortar.  Pt,  Ir,  Pd  are  white,  hard,  very 
heavy,  insoluble  in  acids;  Fe,  Ni,  Co,  are  gray  and  magnetic. 
See  7,  11. 

8.  If  no  incrustation,  no  regulus,  no  white  residue,  but  only 
a DARK  COLORED  residue  remains,  touch  it  with  a good 
BORAX  BEAD  and  fuse  again.  If  the  bead  is  BLUE,  hot  or 
cold,  outer  or  inner  flame,  Co;  if  DEEP  GREEN  under  all  con- 
ditions, Cr;  if  hot  green,  cooling  turns  blue,  Cu;  BROWN, 
Ni;  AMETHYST  in  outer,  colorless  in  inner  flame,  Mn;  YEL- 
LOWISH to  ORANGE  in  outer,  colorless  or  very  pale  green  in 
inner  flame,  Fe.  Compare  7,  11. 

9.  MICROCOSMIC  SALT,  NaAmH  O4P  + 4 H2O,  when 
heated  in  the  platinum  loop,  becomes  metaphosphate  Na  O3P 
which,  like  borax,  dissolves  metallic  oxides  and  gives  colored 
beads.  We  use  these  beads  exclusively  to  recognize  silicates 
and  the  chloroid  compounds.  The  first  leave  an  insoluble 
SKELETON  OF  SILICA  (10.5;  11,  4)  floating  in  the  melted 
bead.  To  test  for  the  latter,  first  saturate  the  bead  with 
copper  oxide,  then  add  a trifle  of  the  substance  to  be  tested; 
flame  colorations:  blue,  Cf^®;  blueish  green.  Bride;  intense 
green,  loide.  Bead  heated  in  glass  tube,  making  inside  dim 
(after  washing) , Ffde. 

10.  SULPHATES,  when  mixed  with  pure  soda  and  fused  on 
platinum  loop  in  inner  flame,  are  reduced  to  sulphides;  the 
fused  mass  placed  on  a silver  coin,  with  a drop  of  water, 
blackens  the  silver,  at  least  if  a trace  of  muriatic  acid  is  added 
(HEPAR  reaction).  SULPHIDES  give  the  odor  of  burning 
sulphur  (9.3).  NITRATES  and  CHLORATES  deflagrate  on 
charcoal,  the  latter  especially  violently.  CARBONATES  are 
best  recognized  by  effervescence  with  an  acid.  BORATES 
tinge  the  flame  green  on  its  outer  edges,  especially  on  adding 
a drop  of  HFl-Si^te.  These  are  the  principal  pyrognostic  re- 
actions. Oxides  give  no  reactions  as  negatives;  they  are 
recognized  by  their  physical  properties  after  other  negatives 
are  proved  absent. 


54.  WET  WAY  ANALYSIS  OF  BASES. 


1.  In  lecture  22  the  metals  were  separated  into  8 analyti- 
cal groups,  mainly  by  the  use  of  hydrogen  sulphide  gas,  and 
each  metal  was  individually  recognized  by  the  specific  peculi- 
arities of  the  group  reaction.  We  need  only  to  add  the  most 
important  DISTINCTIVE  TESTS  and  a few  specially  delicate 
tests  whereby  TRACES  of  the  metals  may  be  detected. 
Methods  of  SEPARATION  will  also  be  indicated.  We  take  up 
the  metals  by  analytical  groups. 

2.  THE  GOLD  GROUP  is  precipitated  by  H in  acid 
solution,  the  precipitate  is  soluble  in  yellow  ammonium  sul- 
phide; the  original  solution  is  yellow  to  brownish. 

GOLD  is  precipitated  as  metallic  powder  by  a ferrous  solu- 
tion (best  the  ferrous  salt,  15,  11);  the  precipitate  appears 
brown  in  reflected,  bluish  in  transmitted  light;  the  dried  pre- 
cipitate shows  metallic  luster  when  pressed  with  a knife  blade. 
Platinum  is  not  precipitated  by  this  reagent,  except  upon 
boiling. 

PLATINUM  solutions,  when  not  too  dilute,  and  containing 
H Glide*  yield  a yellow  precipitate  with  Am  Cfde,  forming 
splendid  transparent  yellow  octahedral  crystals,  which  can  be 
studied  under  the  magnifier  or  the  microscope.  Ignition  leaves 
Pt  sponge.  51.9. 

3.  THE  ARSENIC  GROUP  is  distinguished  from  the  gold 
group  by  its  solutions  being  colorless.  The  dry  way  reactions 
are  especially  valuable  (53,  4,  6).  The  most  sensitive  test 
for  ANTIMONY  is  given  37,  5;  its  solutions  are  also  noted  for 
giving  a white  turbidity  with  water,  which  promptly  dissolves 
upon  the  addition  of  tartaric  acid.  Stannous  solutions  are 
precipitated  white  by  mercuric  chloride;  stannic  solutions  not. 
Stannous  solutions,  containing  a little  stannic,  (on  addition  of 
Cl -water)  give  purple  of  Cassius  with  gold  solutions.  Fur- 
ther special  tests  for  As  belong  to  toxicology. 


244 


LECTURE  54. 


4.  THE  COPPER  GROUP  is  precipitated  by  hydrogen  sul- 
phide in  acid  solutions,  and  the  precipitate  is  insoluble  in  yel- 
low ammonium  sulphide.  Only  Cu  is  slightly  soluble  in 
this  solvent. 

Am  Hate  precipitates  all ; the  white  precipitates  of  Hg’c  and 
Bi  are  insoluble  in  excess;  the  blue  precipitate  of  copper  dis- 
solves to  sky  blue  solution,  the  white  precipitate  of  cadmium 
dissolves  to  colorless  solution  with  excess. 

The  hydrates  precipitated  by  Ka  Hate  are  all  insoluble  in 
excess;  Cd,  Bi  white,  Hgic  brown,  with  excess  yellow  and 
in  presence  of  ammonia,  white;  Cu,  light  blue,  on  boiling 
black. 

The  iodides,  see  23,  11.  Wet  way  reductions  (20,  6)  show 
best  in  reflected  light  under  the  microscope:  Bi  acicular  gray, 
Cd  mosslike  gray;  Cu  mosslike  red  crystals.  See  also  pyro- 
gnostics. 

Bi  solutions  give  white  turbidity  with  water,  not  soluble  in 
tartaric  acid,  only  soluble  in  mineral  acids.  Copper  solutions, 
even  if  extremely  dilute,  give  a brownish  precipitate  with  Ka 
Cyo  Feate  solutions. 

5.  THE  SILVER  GROUP  reacts  towards  H Side  and  yellow 
ammonium  sulphide  exactly  as  the  copper  group,  from  which 
it  differs  by  being  precipitated  by  H CPde  or  any  other  soluble 
chloride.  See  22,  Note  1.  Iodides,  see  23,  11. — Ka  Crate 
precipitates  Ag  deep  purplish  red;  Hgous  brick  red;  Pb  bright 
yellow,  soluble  in  Ka  Hate,  but  difficultly  soluble  in  dilute  nitric 
acid.  Ka  Hate  precipitates  the  hydrates:  Ag,  light  brown, 
Hgous  black,  both  insoluble  in  excess  (Ag  Hate  soluble  in  aqua 
ammonia  to  explosive  compound)  ; Pb  white,  soluble  in  excess, 
no  immediate  precipitate  in  presence  of  acetic  acid.  Pyrog- 
nostic,  see  53. — Wet  way  reductions,  very  fine:  Ag,  arbor- 
escent, white  crystals;  Pb,  acicular  gray  crystals;  Hg,  on 
copper,  silvering,  volatilized  by  heat. 

G.  The  zinc  group  is  not  precipitated  by  H Side  gas  in 
acid  solution,  but  like  the  aluminium  group,  precipitated  there- 
by in  alkaline  solutions;  it  is  distinguished  from  the  aluminium 


WET  WAY  ANALYSIS  OF  BASES. 


245 


group  by  its  hydrates  being  soluble  in  sufficient  Am  solu- 
tion. The  pyrognostic  tests  on  charcoal  and  borax  beads  are 
specifically  distinctive  (Lect.  53).  Mn  on  soda  bead,  GREEN 
mass  (manganate)  dissolves  in  acid  solution  to  purplish  per- 
manganate. 

Potassium  hydrate  precipitates  all,  an  excess  dissolves  Zn 
only;  from  this  solution,  H reprecipitates  the  Zn,  but  Am 
Cl'de  does  not  (distinction  from  Al).  The  Mn  precipitate, 
white,  turns  dark  brown;  Feous  white,  turns  promptly  green- 
ish, then  rust  brown;  Ni  light  green,  unchanged,  dissolved  by 
Am  to  greenish  blue  solution;  Co,  blue  precipitate,  turns 
green,  on  boiling  reddish,  is  soluble  in  Am  to  brownish 
red  solution. 

Feous  solutions,  even  if  extremely  dilute,  are  precipitated 
deep  blue  by  Ka  Cy'  Fe^t©  (red  prussiate  of  potash),  while 
the  Ka  Cyc»  Fe^te  (yellow  prussiate)  give  bluish  white  pre- 
cipitate, turning  gradually  deep  blue  in  air. 

7.  THE  ALUMINIUM  GROUP  is  characterized  as  just  stated 

under  6,  its  hydrates  being  insoluble  in  Am  The  pre- 

cipitate with  H Sid®  in  alkaline  solutions  is  the  hydrate,  not  a 
sulphide.  See  22,  10. 

Ka  Hate  gives  a precipitate  in  all  cases:  Al,  white,  readily 
soluble  in  excess,  reprecipitated  by  Am  Cbde,  not  by  H Side 
(distinction  from  Zn) ; Ci'i®  greenish,  soluble  in  excess,  repre- 
cipitated by  Am  Cbde  OR  by  protracted  boiling;  Feic>  brown 
precipitate,  not  soluble  in  excess. — See  Pyrognostic  reactions, 
Lect.  53,  and  group  tests,  Lect.  22. 

Ferric  solutions,  even  if  extremely  dilute,  give  with  Ka  Cy® 
Feate  the  deep  blue  precipitate  (Prussian  blue),  insoluble  in 
H Clide,  readily  soluble  in  Ka  Hate — With  Ka  Cyi  Feate,  no 
precipitate.  With  Ka  S-Cyate,  deep  blood  red  coloration, 
destroyed  by  Ka  Acetate,  restored  by  H Cbde;  color  dissolved 
in  ether.  Extremely  sensitive  reaction.  Cr  compounds, 
fused  with  soda  and  nitre  on  loop,  give  chromate,  yellow. 

8.  THE  BARIUM  AND  MAGNESIUM  GROUPS  remain  in 
solution,  if  the  treatment  with  H Sate  (Lect.  22)  has  been 


246 


LECTURE  55. 


omitted.  In  the  case  of  mixtures,  it  is  best  so  to  do;  but  in 
case  of  presence  of  phosphates,  the  previous  precipitation  as 
sulphate  has  advantages. 

If  no  sulphate  has  been  added,  the  second  group  (Ca,  Sr, 
Ba)  is  precipitated  as  in  the  first  reaction  of  VIII;  the 
precipitate  removed  by  filtration,  the  precipitate  may  be  tested 
for  members  of  second  group  by  flame  (53,  3)  and  spectrum 
(52,  6)  while  the  filtrate  is  worked  up  as  directed  in  Lect.  22, 
Note  5. 

9.  THE  PRESENCE  OF  PHOSPHATES,  oxalates,  silicates, 
borates  and  fluorides,  singularly  complicates  the  analytical 
separation  of  the  last  two  groups  (our  II  and  Vlll).  When  the 
solution  is  made  alkaline,  previously  to  the  precipitation  of  the 
zinc  and  aluminium  groups,  such  phosphates,  etc.,  of  the 
barium  group  go  down,  and  will  be  found  in  the  precipitate  of 
VI,  VII.  By  means  of  Ba  a separation  is  effected,  but 
the  operations  are  too  complicated  for  the  present. 

10.  SEPARATION  of  the  different  groups  is  effected  by  the 
group  reactions  given.  Separation  of  members  in  a group 
depends  on  the  individual  characters  given  in  this  lesson. 
Thus  Fe’*^  is  separated  in  VII  from  A1  by  Ka  H^te;  Cd  and  Cu 
from  Hgic  and  Bi  in  III  by  excess  of  Am  Hate;  pb  from  Ag 
and  Hgous  in  I by  water,  and  Ag  from  Hgous  in  the  washed 
precipitate  by  Am  Hate.  Such  work,  however,  is  specially 
restricted  to  the  Laboratory  Stands. 


55.  WET  WAY  ANALYSIS  OF  ACIDS. 

1.  Having  found  the  metallic  constituent  (27.5)  in  the 
given  compound,  the  known  SOLUBILITY  of  the  compound 
examined  will  often  enable  us  to  exclude  quite  a number  of 
acids  or  non-metallic  constituents,  so  as  to  limit  our  search  to 
those  possibly  present. 

2.  Thus,  if  LEAD  has  been  found  in  a compound  soluble  in 
water,  it  cannot  possibly  be  the  carbonate,  sulphate,  chro- 


WET  WAY  ANALYSIS  OF  ACIDS. 


247 


mate,  sulphide,  oxide,  chloride,  iodide;  for  these  lead  com- 
pounds are  all  insoluble  in  water,  as  may  be  remembered  from 
previous  lessons.  If  the  lead  compound  examined  had  been 
insoluble  in  water,  any  of  the  above  acids  might  be  present, 
but  nitrate  and  acetate  could  not  be,  since  lead  nitrate  and 
acetate  are  soluble  in  water. 

3.  Accordingly  it  is  important  to  be  able  to  tell  what  com- 
pounds are  soluble  in  water,  and  which  are  insoluble  therein. 
For  neutral  compounds,  the  following  simple  RULES  OF  SOL- 
UBILITY will  answer  all  practical  purposes: 

4.  SOLUBLE  are  nearly  all  the  salts  of  Na,  Ka  and  Am; 
also  Nitrates,  Chlorates  and  Acetates. 

SOLUBLE  are  the  Carbonates,  Phosphates,  Silicates  and 
Oxalates  of  Na,  Ka  and  Am. 

SOLUBLE  are  the  Hydrates,  Oxides  and  Sulphides  of  Na, 
Ka  (Am)  and  Ca,  Sr,  Ba. 

INSOLUBLE  are  the  Sulphates  of  Ca,  Sr,  Ba  and  Pb;  the 
Chromates  of  Ba,  Pb,  Ag,  Hg,  Bi. 

INSOLUBLE  are  the  Chlorides  of  Ag,  Hgous  pb;  also  the 
Iodides  of  same  and  of  Hgic  and  Bi. 

5.  Those  non-metallic  constituents  which  yield  a gas 
(effervesce)  upon  the  addition  of  a non-volatite  acid,  will 
have  been  detected  while  testing  for  groups  I and  II  (p.  146). 
If  the  effervescence  is  odorless,  and  yields  turbidity  with  lime 
water,  it  is  a carbonate.  If  the  effervescence  exhibits  the 
odor  of  burning  sulphur,  it  is  a sulphite;  rotten  eggs,  a sul- 
phide; peach  blossoms,  a cyanide. 

G.  Chromates,  Manganates,  Permanganates,  Arsenates 
and  other  salts  containing  a heavy  metal  and  forming  ME- 
TALLO-SALTS  reveal  themselves  by  a separation  of  sulphur 
(p.  146.3)  when  the  acid  solution  is  saturated  with  hydrogen 
sulphide  gas.  At  the  same  time,  the  color  of  the  solution 
often  changes.  Thus  Chromates,  being  yellow  or  red,  change 
to  green;  Manganates  are  green  and  turn  brownish;  Perman- 
ganates turn  from  purplish  to  brownish. 


248 


LECTURE  55. 


7.  If  the  non -metallic  constituent  has  not  been  indicated 

by  these  reactions  made  in  the  course  of  examination  for  the 
metal,  the  following  REAGENTS  are  used:  Ba  N^te,  Ca  S^te 
and  Ag  detecting  respectively  Sulphate,  the  Phosphate 

group  and  the  Chloride  group.  If  no  precipitate  obtained,  the 
Nitrate  group  is  present. 

8.  If  the  original  solution  acidified  with  nitric  acid  gives  a 
precipitate  with  Barium  Nitrate,  the  compound  is  a SULPHATE. 
This  precipitate,  taken  up  in  a soda  bead,  and  exposed  to  the 
inner  flame  of  the  blowpipe,  will  stain  a silver  coin  black  upon 
the  addition  of  a drop  of  water  or  muriatic  acid,  under  the 
evolution  of  hydrogen  sulphide  gas,  readily  recognized  by  its 
odor.  This  is  the  so-called  hepar  test. 

9.  If  the  neutral  or  slightly  alkaline  solution  of  the  sub- 
stance examined  yields  a white  precipitate  with  Calcium  Sul- 
phate, the  PHOSPHATE  GROUP  of  acids  is  present.  If  the 
precipitate  upon  the  addition  of  acetic  acid  dissolves,  it  is  a 
phosphate  (compare  p.  14:6,  5-6)  ; if  it  does  not,  it  is  an 
oxalate.  The  other  acids  (Silicate  and  Fluoride)  are  most 
readily  detected  in  the  dry  way  (10.5;  11,  4). 

10.  If  no  precipitate  yet  obtained,  another  portion  of  the 
original  solution  is  acidified  with  nitric  acid  and  a few  drops  of 
silver  nitrate  are  added;  a curdy  precipitate  indicates  the 
CHLORIDE  GROUP.  The  precipitate  is  separated  and  washed 
by  decantation,  and  treated  with  strong  ammonium  hydrate, 
to  ascertain  whether  the  curdy  precipitate  is  soluble  or  not 
therein.  In  the  latter  case,  it  is  an  IODIDE. 

11.  If  soluble,  it  is  either  BROMIDE  or  CHLORIDE  (for 
cyanide  would  have  been  detected  in  5).  If  the  original  so- 
lution with  chlorine  water  turns  yellowish,  and  if  upon  shak- 
ing with  chloroform  this  turns  orange  while  the  aqueous 
solution  becomes  colorless,  a bromide  is  present;  if  not,  the 
substance  is  a chloride. 

12.  If  no  precipitate  so  far  obtained,  the  given  compound  is 
a Nitrate,  Acetate  Chlorate  or  Borate.  An  excess  of  concen- 


WET  WAY  ANALYSIS  OF  ACIDS. 


249 


trated  sulphuric  acid  being  added:  to  one  portion  add  copper 
turnings,  rutilant  vapors  prove  the  Nitrate;  to  another  add  a 
few  drops  of  alcohol,  the  odor  of  acetic  ether  indicates  acetates. 
If  neither  of  these,  add  a drop  of  concentrated  sulphuric  acid 
to  a small  fragment  of  the  substance - yellow,  chlorous  gas 
evolved  proves  the  CHLORATE. 

If  no  such  odor  or  gas,  try  flame  coloration ; if  outer  mantle 
green,  the  substance  is  a BORATE. 

If  all  these  reactions  failed  to  give  a positive  result,  the 
substance  is  an  oxide  or  hydrate,  to  be  recognized  by  its 
physical  characters. 


56.  RECOGNITION  OF  SPECIMENS. 

1.  This  concludes  the  introduction  to  inorganic  chemistry. 
If  this  course  has  been  complemented  by  laboratory  work,  the 
student  now  is  fairly  familiar  with  the  most  important  SUB- 
STANCES, FACTS  AND  PRINCIPLES  of  inorganic  chemistry. 

2.  He  will  have  acquired  the  important  ability  of  the 
RECOGNITION  OF  SPECIMENS  of  minerals  and  chemical 
compounds,  mainly  by  their  physical  properties,  but  aided  by 
simple  chemical  tests  made  either  by  the  blowpipe,  or  by  a 
drop  of  a dozen  or  two  of  reagents  applied  to  the  minute 
sample  in  a watchglass  or  on  a microscope  slide. 

3.  The  MICROCHEMICAL  REAGENTS  for  this  sort  of 
testing  in  the  wet  way  are  kept  in  small  bottles  with 
pipette  and  ground  glass  cap,  or  cork  stoppered,  the  stopper 
carrying  from  below  a short  piece  of  glass  rod  dipping  in  the 
liquid.  Of  course,  the  drop  taken  must  be  placed  on  clean 
glass,  near  the  drop  or  substance  to  be  acted  upon,  to  prevent 
contamination  of  the  reagent.  By  a working  glass  rod  the 
mixture-  is  effected. 

4.  The  necessary  SULPHURETTED  HYDROGEN  GAS  is 
generated  in  a test  tube,  broken  below,  divided  into  two  equal 
compartments  by  a perforated  cork  disk,  and  inserted  into  a 


250 


LECTURE  56. 


cylinder  or  salt  mouth  flask  with  dilute  muriatic  acid.  The 
tube  is  held  at  any  desired  depth  by  means  of  a cork  wedge. 
The  upper  compartment  contains  a couple  of  pieces  of  iron 
sulphide,  and  is  closed  by  a cork,  through  which  passes  a 
glass  tube  connected  with  rubber  tube  and  spring  clamp. 
To  the  rubber  attach  the  delivery  tube. 

5.  Depressing  the  tube  starts  the  GENERATION  OF  THE 
GAS,  only  a few  bubbles  of  which  are  required  at  a time. 
When  not  at  work,  be  sure  to  have  the  cork  partition  a centi- 
meter above  the  level  of  the  acid.  Such  a little  apparatus  is 
a perfect  substitute  of  the  Kipp  generator  for  the  elementary 
microchemical  work  here  contemplated. 

6.  THE  TABLES  given  in  this  text  (Lectures  22,  53,  54, 
55),  are  sufficient  for  the  beginner.  A minute  fragment  of 
the  solid  is  all  the  MATERIAL  REQUIRED  for  testing.  A few 
watch  glasses  and  microscope  slides  take  the  place  of  the  test 
tubes,  beakers  and  flasks.  A few  pieces  of  hard  (Bohemian) 
glass  tubing  and  an  alcohol  lamp  (glass)  will  permit  to  add 
dry  way  work.  The  work  is  most  interesting  and  instructive. 

7.  FOR  EXAMPLE,  a small  prismatic  crystal  is  given  for 

recognition.  A portion  thereof,  in  a watch  glass,  dissolves- 
readily  in  a drop  of  water.  Dots  made  with  this  solution  are 
placed  on  a microscope  slide  (or  slides).  With  H and 
H S^te,  no  Pr;  these  with  the  sulphide  gas  give  Pr,  first  y, 
then  bn,  finally  bk;  Pr  with  drop  of  water,  run  off,  leaves 
residue  insoluble  in  drop  of  yellow  Am  evidently  Hgi^^ 

compound.  Confirm  by  Ka  lo’^^’  Cu,  etc. 

Excluded  are  acids:  C^te,  etc.;  H^te,  etc.;  Cr^te,  loide. 
No  effervescence,  no  volatile  acid.  Dot  acidified  with  a touch 
of  dil.  H N^te  gives  no  Pr.  with  Ba  Sol;  P^te  group  excluded 
on  account  of  insolubility;  another  acidified  dot  with  a touch 
of  Ag  gives  white  curdy  Pr — readily  sol.  Am  Hate,  hence 
either  Cf^e  of  Br’^e,  since  Cyi^e  proved  absent — BH^e  test 
made  in  watch  glass  with  single  drops  shows  no  BF^e  reaction. 
Hence,  crystal  was  Hgic  Cfde,  CORROSIVE  SUBLIMATE. 


RECOGNITION  OF  SPECIMENS. 


251 


8.  RECOGNITION  OF  COMMON  MINERALS  should  be 
practiced  on  small  fragments,  and  cleavage  pieces ; the  greatest 
dimension  need  not  exceed  one  centimeter,  so  that  a large 
number  of  specimens  can  be  given  in  a small  paper  tray  or  an 
ordinary  specimen  tube.  Hardness  should  be  determined  by 
the  nail,  copper,  glass  and  file.  Gravity  need  not  be  actually 
determined,  if  blowpipe  or  microchemical  tests  applied,  or  if 
the  work  is  restricted  to  the  most  common  minerals. 

9.  If  determinations  of  the  specific  gravity  are  wanted, 
make  a HYDROSTATIC  BALANCE,  by  replacing  one  horn  pan 
of  the  common  German  hand  scale  by  a double  pan  of  wire 
gauze  held  about  8 or  10  cm.  apart  by  brass  wires;  the  lower 
of  these  pans  being  submerged  in  the  water  of  a small  crystal- 
lizing dish.  For  weights,  use  common  block  weights  from  10 
gr.  to  1 cgr.  Weigh  specimen  in  air  on  upper,  in  water  on 
lower  wire  gauze  pan. 

10.  CLEAVAGE  pieces  frequently  permit  good  determina- 
tions by  means  of  our  goniometer,_  p.  68.  Thus  Barite  and 
Celestite  give  right  rhombic  cleavage  pieces.  For  Barite  the 
angle  of  the  prism  is  less  than  102  degrees  (11,  9);  but  for 
Celestite  this  angle  is  104  degrees,  a difference  easily  recog- 
nized. In  fact,  Hauy  distinguished  these  mineral  species  by 
this  notable  difference,  before  strontium  was  known,  a feat 
comparable  to  modern  distinctions  by  spectrum  lines.  (Traite, 
T.  2,  318-326;  Paris,  1801). 

11.  A DIAGRAM  on  which  the  leading  mineral  species  are 
located  according  to  their  G and  H as  horrizontal  and  vertical 
dimensions,  (co-ordinates)  is  very  useful  for  the  recognition  of 
minerals.  Thus,  at  about  H 6 and  G 5 are  located  three 
species  only,  namely  Pyrite,  Hematite  and  Magnetite.  But 
the  first  is  readily  distinguished  by  its  brilliant  metallic  luster 
and  yellpw  color  (9,  8),  while  the  last  two  are  distinguished 
by  their  streak  (9,  6) . 

12.  On  such  a diagram,  the  species  of  a genus  form  some 
definite  curve,  showing  that  the  PHYSICAL  PROPERTIES  ARE 


252 


LECTURE  57. 


DEFINITE  FUNCTIONS  OF  THE  METAL.  Thus  the  sul- 
phates R O4S  in  which  R is  Ca,  Sr,  Ba,  Pb  form  the  definite 
curve  parallel  to  and  a little  below  the  curve  for  the  corres- 
ponding carbonates  R O3C,  which  are  about  half  a degree 
harder.  The  author  has  found  work  of  this  character  far 
superior  to  the  common  study  of  systematic  chemistry. 


57.  ORGANIC  PRIME  MATERIALS. 

1.  Minerals  constitute  the  body  of  the  earth.  Together 
with  the  water  of  the  ocean  and  the  gases  of  the  atmosphere, 
they  have  furnished  the  prime  materials  for  our  chemical  in- 
vestigations. Thus  far,  we  have  studied  inorganic  chemistry 
only. 

2.  Under  the  action  of  the  light  and  heat  of  the  sun  upon 
the  air  and  moisture,  the  surface  of  the  earth  has  been  covered 
with  plants.  Attached  to  the  mineral  world  by  their  roots 
ramifying  in  the  soil,  they  push  stem  and  branches  up  into  the 
air  and  unfold  their  leaves  to  the  sunbeam  which  every  season 
calls  forth  flowers  and  fruits  as  the  highest  forms  of  VEGETA- 
BLE MATTER. 

3.  Almost  every  portion  of  vegetable  matter  is  utilized  by 
animals  as  food.  To  secure  this,  animals  are  endowed  with  a 
power  of  voluntary  motion.  Vegetable  matter  is  transformed 
by  the  animal  into  bone,  muscle  and  nerve;  also  into  egg, 
blood  and  milk.  Such  substances  are  ANIMAL  MATTER. 

4.  The  whole  earth  becomes  more  and  more  the  GARDEN 
OF  MAN.  “Out  of  the  ground  grow  trees  pleasant  to  the 
sight  and  good  for  food.”  Man  is  getting  a more  complete 
“dominion  over  the  fish  of  the  sea,  over  the  fowl  of  the  air, 
and  over  every  living  thing  that  moveth  upon  the  earth.” 
But  the  earth  “brings  forth  thorns  also  and  thistles,”  so  that 
“man  eats  his  bread  in  the  sweat  of  his  face.”  Genesis,  1-3. 


ORGANIC  PRIME  MATERIALS. 


5.  Plants  and  animals  furnish  the  prime  materials  for  or- 
ganic chemistry,  as  minerals  do  for  inorganic  chemistry. 
ORGANIC  CHEMISTRY,  in  its  broadest  sense,  treats  of  the 
changes  of  matter  of  the  organic  world. — 1.  5-7. 

G.  The  starchy  grain,  when  germinating,  becomes  soft, 
sweetish,  gummy;  a new  plant  grows  from  it.  In  the  leaves 
of  this  new  plant  we  notice  green  coloring  matter,  woody  cell 
tissue,  acids;  at  least  during  flowering,  volatile  substances  are 
formed;  then  new  grains  make  their  appearance,  at  first  gum.- 
my,  then  sweetish,  finally  starchy.  Such  a cycle  of  changes 
is  a subject  for  investigation  in  organic  chemistry;  its 
LABORATORY  IS  THE  CELL,  its  power,  the  Sun. 

7.  This  new  grain,  mixed  with  malted  barley,  changes  to 
a sugar ; exposed  to  the  ferments  of  the  air,  it  produces  alcohol ; 
this  is  readily  converted  into  thousands  of  new  materials, 
such  as  acetic  acid,  aldehyd,  chloral,  chloroform  and  ethers. 
Many  such  processes  have  for  centuries  been  practiced  on  a 
large  scale;  they  are  OPERATIONS  OF  ORGANIC  CHEMIS- 
TRY. 

8.  Organic  matter  contains  carbon,  as  is  readily  shown  by 
the  simple  test  of  charring  (1,  5),  which  also  generally  per- 
mits us  to  distinguish  animal  from  vegetable  matter.  Accord- 
ingly, modern  chemists  have  defined  organic  chemistry  as  the 
chemistry  of  carbon  compounds,  ostensibly  to  maintain  the 
unity  of  the  science  of  chemistry;  but  the  innovation  is 
rather  narrow. 

9.  As  a matter  of  fact,  the  products  of  the  soil  throughout 
the  world  and  their  modifications  by  animals  furnish  almost 
exclusively  the  PRIME  MATERIALS  OF  ORGANIC  CHEMISTRY. 
In  the  economy  of  nations,  these  products  alone  are  of  import- 
ance. To  increase  their  production,  to  improve  their  quality, 
and  multiply  their  forms  of  application,  marks  the  main  work- 
ing field  of  organic  chemistry.  In  this  field  the  United  States 
are  prominent. 


254 


LECTURE  58. 


10.  In  the  course  of  the  chemical  changes  of  these  prime 
materials,  many  NEW  and  valuable  PRODUCTS  are  obtained, 
first  in  the  laboratory  and  afterwards  in  the  factory.  But  in 
nearly  all  cases,  these  new  substances  either  are  identic  with 
or  correspond  to  substances  furnished  by  plant  or  animal,  and 
often  were  already  used  by  the  ancients. 

11.  This  is  especially  striking  regarding  the  COAL-TAR 
PRODUCTS,  the  investigation  of  which  has,  in  some  regions, 
almost  monopolized  the  efforts  of  the  chemist.  This  inevita- 
ble one-sidedness  has  led  to  systematic  errors,  and  boastful 
assertions  of  superiority  as  unfounded  as  they  are  unbecoming. 

12.  Hasty  conclusions,  unwarranted  generalizations  and 
bulky  publications  have  marred  the  work  of  the  last  quarter 
century.  THE  CHEMICAL  PRESS  has  become  rather  sensa- 
tional, not  merely  in  its  diagrams  and  long  names.  In  real 
science,  we  need  more  earnest  thought,  less  haste;  more 
grain,  less  straw  in  our  publications.  In  our  industry  and 
intercourse,  less  of  the  modern  “survival  of  the  fittest,”  a 
heartless  philosophy  of  doubtful  foundation ; more  of  a revival 
of  the  moral  code  and  the  golden  rule. 


58.  SUGAR  AND  WINE. 

1.  The  tall  SUGAR  CANE  has  its  home  in  Asia  (India  and 
China).  The  Arabs  planted  it  in  Italy  and  Spain.  Since  it 
has  found  its  most  extended  cultivation  in  America,  from  Cuba 
to  Brazil.  The  juice  (90  per  cent.)  of  the  ripe  cane  is  sweet; 
it  is  a strong  sulution  (10  to  18  per  cent.)  of  true  sugar,  the 
SUCROSE  of  modern  chemistry. 

2.  The  juice  is  pressed  out  by  passing  the  cane  between 
revolving  cylinders.  Gentle  heating  with  a little  lime  removes 
impurities.  Concentration  in  (open  and  vacuum)  pans  gives 
crude  sugar  in  crystals,  and  molasses.  In  the  refineries  of 
Europe  and  the  United  States  (14,  11),  the  pure,  crystallized 


SUGAR  AND  WINE. 


255 


sugar  is  obtained.  Tropical  America  produces  one  and  one- 
half  million  tons.^  Asia,  Africa  and  Australia  one  million  tons. 
Total,  two  and  one-half  million  tons  of  cane  sugar  a year. 

3.  SUGAR  (sucrose)  is  a white  solid  without  odor.  G 1.6; 
F 160,  solidifying  to  a white,  amorphous,  vitreous  mass,  grad- 
ually becoming  opaque  and  again  crystalline.  At  higher  tem- 
peratures it  chars  and  burns. 

Sugar  is  soluble  in  half  its  own  weight  of  cold  water,  and  in 
all  proportions  in  hot  water.  From  its  solution  it  crystallizes 
in  oblique  rhombic  prisms  (M  M'  101.5  and  M P 98.5)  called 
Rock  candy.  The  Maple  sugar  of  New  England  is  also 
mainly  sucrose. 

4.  The  same  sugar  (sucrose)  was  discovered  by  Marggraf 
of  Berlin  in  the  juice  of  the  beet  (1747).  About  1830  France 
had  50  beet  sugar  factories;  twenty  years  later  the  beet  sugar 
production  had  taken  root  in  Germany  and  Austria.  These 
two  countries  now  produce  two  million  tons  of  BEET  SUGAR, 
while  the  balance  of  Europe  produces  one  and  one-half  million 
tons  only.  Total,  three  and  one-half  million  tons  of  beet 
sugar  a year  (1889-90). 

5.  Honey  and  Manna  were  the  only  SWEET  SUBSTANCES 
known  in  antiquity,  even  to  the  Greeks.  The  Hindoos  had 
extracted  sucrose  from  the  cane,  500  B.  C.  The  Arabs 
brought  sucrose  to  Southern  Europe.  With  the  importation  of 
slaves,  cane  planting  began  in  tropical  America.  During  the 
last  forty  years,  chemistry  has  profoundly  modified  agriculture 
in  Central  Europe,  which  now  extracts  more  sucrose  from  the 
beet  root  than  is  produced  in  the  sugar  cane  of  the  tropics. 

6.  States,  recognizing  the  economic  advantages  of  increas- 
ing and  diversifying  the  industries,  have  at  all  times  fostered 
new  industries  by  SPECIAL  LEGISLATION.  The  history  of 
the  beet  sugar  industry  shows  the  marvellously  stimulating 
effect  of  such  legislation,  but  also  the  depression  that  seems 
an  unavoidable  sequence.  Europe  now  is  in  the  latter  stage. 


256 


LECTURE  58. 


while  we  are  entering  upon  the  first  stage  by  voting  a bonus 
upon  the  production  of  all  sugar. 

7.  Ripe  GRAPES  taste  sweet;  but  no  sucrose  can  be 
extracted  from  them.  When  dried  (raisins),  the  sweet  prin- 
ciple appears  as  a gritty  solid,  called  grape  sugar  or  GLUCOSE. 
It  promptly  reduces  the  boiling  Fehling-Solution  (an  alkaline 
tartrate  of  copper)  giving  a red  precipitate  of  cuprous  oxide. 
Afresh  sucrose  solution  gives  no  precipitate;  hence  the  im- 
portance of  this  test.  Figs  and  many  other  fruits  give  the 
same  reaction;  so  does  honey;  they  contain  glucose. 

8.  When  ripe  grapes  are  piled  up,  they  burst  under  their 
own  weight;  the  rich,  sweet  juice  or  must  (95  per  cent,  of 
berry)  runs  out.  Set  aside  in  filled  vessels,  it  undergoes  a 
remarkable  change,  called  FERMENTATION,  during  which 
much  fixed  air  (16.8)  is  given  off.  Finally,  the  liquid  becomes 
clear  again:  it  is  WINE,  the  special  product  of  the  white  race, 
the  milk  of  old  age  that  ought  to  be  but  sparingly  used  by  the 
young. 

9.  WINE  MAKING  is  probably  the  oldest  chemical  industry. 
The  patriarchs  made  wine  and  drank  it.  The  Egyptian 
monuments  show  the  cutting  of  the  grapes  from  the  trellises, 
and  the  pressing  of  the  must.  The  Greeks  and  Romans  held 
wine  in  high  esteem.  Among  modern  nations,  the  French 
produce  the  most,  over  2,000  million  gallons  a year  before  the 
phylloxera  came,  and  about  800  million  gallons  a year  during 
the  last  10  years.  Spain,  Italy  and  Germany  come  next. 
In  America,  California  has  long  been  foremost,  both  in  amount 
(12  million  gallons)  and  quality  of  the  wine  produced. 

10.  Slow  distillation  of  wine  yields  a very  volatile  liquid, 
known  in  the  13th  century  as  AQUA  VIT/E  and  used  as  a 
medicine,  to  which  the  most  extravagant  virtues  were  ascribed. 
This  is  our  brandy.  The  finest  is  produced  in  France  (Cognac) . 
California  also  manufactures  good  brandy  in  large  quantities. 
Its  specific  gravity  should  range  between  0.92  and  0.9T.  It  is 
readily  inflammable,  burning  with  a pale  blue  flame,  leaving  a 
liquid  residue. 


SUGAR  AND  WINE. 


257 


11.  Subjecting  brandy  to  fractional  distillation,  the  most 
volatile  fractions  become  lighter  and  more  completely  com- 
bustible (spirits).  When  the  specific  gravity  is  reduced  to 
about  0.82,  the  liquid  is  properly  called  ALCOHOL.  By  care- 
ful distillation  it  can  be  brought  down  to  0.81  When  distilled 
from  quick  lime  (after  a day*s  contact  therewith  in  a closed 
vessel),  the  distillate  may  be  brought  down  to  0.79,  boiling  at 
78.°4.  This  is  ABSOLUTE  ALCOHOL,  solidifying  at  - 130  de- 
grees. It  is  extremely  hygroscopic. 

12.  The  alcohol  of  0.82  contains  94  per  cent,  of  absolute 
alcohol  by  volume,  91  per  cent,  by  weight;  the  STRENGTH 
OF  AN  ALCOHOL,  containing  only  water  as  diluent,  is  de- 
termined by  its  specific  gravity,  47,  11. 

Alcohol  is  PRODUCED  (for  industrial  purposes)  in  enormous 
quantities  from  various  sources  in  these  days.  In  the  year 
1890-91,  Germany  produced  75  million  gallons,  France  50, 
Russia  100,  Austro -Hungary  50,  England  25;  total  300  million 
gallons  (of  100  per  cent.)  or  a million  gallons  a day.  The 
production  of  the  United  States  is  also  very  great. 


59.  FATS  AND  OILS. 

1.  The  basin  of  the  Mediterranean  Sea,  the  seat  of  civili- 
zation of  antiquity,  is  the  home  of  the  olive  tree.  The  Greeks 
regarded  it  as  a symbol  of  peace,  a gift  of  the  Gods.  Its  wood 
is  hard,  growth  slow,  size  moderate,  foliage  elegant,  flowers 
delicate,  white  and  fragrant,  fruit  fleshy,  containing  half  its 
own  weight  of  the  purest  fatty  oil,  yielding  to  simple  pressure: 
OLIVE  OIL.  It  is  yellowish,  G 0.915,  and  begins  to  solidify 
at  5^ 

2.  The  portion  of  olive  oil  remaining  liquid  at  the  freezing 
point  is  called  OLEIN ; it  amounts  to  about  three -fourths  of 
the  oil.  The  last  traces  of  the  solid  constituent  of  olive  oil  are 
removed  by  repeating  the  process. 


258 


LECTURE  59. 


Olein  remains  liquid  on  exposure  to  the  air;  it  is  a non- 
drying oil.  It  congeals  at  — 6 degrees,  is  soluble  in  ether  and 
in  boiling  alcohol.  Rutilant  vapors  solidify  it;  this  solid 
(elaidin)  melts  at  32  degrees. 

3.  The  solid  residues  of  sweet  oil  are,  by  pressure,  freed 
from  the  olein  adherent,  the  last  traces  of  which  are  extracted 
by  boiling  alcohol;  what  remains  is  called  PALMITIN  or 
margarin.  Crystallized  from  ether,  it  melts  at  61  degrees, 
but  may  be  cooled  to  41  degrees  before  it  solidifies  again. 
Accordingly,  sweet  oil  is  a mixture  of  about  three  parts  of  olein 
and  one  of  margarin.  These  two  fats  are  also  the  constitu- 
ents of  the  fat  of  the  human  body. 

4.  The  hunter  and  herdsman  obtained  the  fat  required  for 
food  from  the  animals  he  captured  or  raised.  The  best,  most 
readily  digested  fat,  is  BUTTER;  it  is  also  the  most  complex, 
so  that  its  consideration  must  be  deferred  for  the  present.  By 
melting  on  a water  bath,  animal  fats  are  obtained  in  the  purest 
form;  especially  TALLOW,  melting  at  45-46  degrees,  from  the 
ox;  LARD,  (38-40  degrees)  from  the  hog,  and  SUET  (50  de- 
grees) from  the  sheep.  Goose  grease  melts  at  25-26  degrees; 
it  does  not  deserve  the  neglect  it  receives  in  modern  medicine, 
which  prefers  inert,  non-assimilable  petroleum  products. 

5.  When  cold  lard  is  subjected  to  hydraulic  pressure,  LARD 
OIL  runs  out  and  a white  solid,  STEARIN,  remains. 

Lard  oil  is  produced  in  enormous  quantities  in  America;  it 
has  the  general  properties  of  olein,  but  betrays  its  hog-origin  by 
instantly  producing  reddish-brown  color  in  contact  with  con- 
centrated sulphuric  acid.  This  coloration  is  evidently  due  not 
to  the  main  body  of  the  lard  oil,  but  to  an  ingredient  present 
in  small  amounts  only. 

6.  The  solid  fat  STEARIN  is  obtained  pure  by  pressing 
purified  suet  at  25  degrees,  dissolving  the  residue  in  its  own 
volume  of  hot  ether,  from  which  stearin  crystallizes  on  cool- 
ing. These  crystals  are  purified  by  pressing,  and  recrystalli- 
zation. 


FATS  AND  OILS. 


259 


Stearin  melts  at  70  degrees;  it  is  but  little  soluble  in  alco- 
hol and  ether  at  common  temperatures;  it  freely  dissolves  in 
boiling  ether.  Suet  contains  one-fifth  olein;  the  balance  is 
margarin  and  stearin. 

7.  FATS  FROM  FISH  are  generally  recognized  by  their 
odor.  A single  whale  (physeter)  will  furnish  80  tons  of  whale 
oil,  mainly  consisting  of  two  liquid  fats,  olein  and  physetolein. 
Cod  Liver  Oil  is  extracted  from  the  liver  of  Gadus  Morrhua 
and  kindred  species  of  gadus.  It  consists  mainly  of  olein; 
owes  its  reputation  to  ingredients  present  in  minute  quantities, 
and  not  yet  fully  known.  A drop  of  concentrated  sulphuric 
acid  produces  a series  of  colors  resembling  the  strychnine 
color  reaction.  See  64,  11. 

8.  Linseed  yield  upon  pressure  a fixed  oil  which,  on  ex- 
posure to  the  air,  dries  to  a varnish.  It  contains  about  20  per 
cent,  of  solid  fats;  no  olein,  but  the  liquid,  drying  linolein 
instead.  Accordingly,  it  does  not  solidify  with  rutilant  vapors. 
By  boiling  with  litharge,  the  drying  qualities  of  the  oil  are  im- 
proved. 

9.  In  general,  fatty  substances  are  greasy  to  the  touch, 
and  non-volatile,  leaving  on  paper  a permanently  transpar- 
ent spot.  They  are  lighter  than  water  (on  which  they  float) ; 
G 0.90  to  0.94.  At  common  temperatures  they  are  either 
solid  (fats)  or  liquid  (OILS).  They  may  be  separated  by 
cold  and  pressure  into  a few  simple  fats  of  perfectly  definite 
properties  (stearin,  margarin,  olein).  They  are  insoluble  in 
water,  partly  soluble  in  (hot)  alcohol,  readily  soluble  in  ether. 
They  are  combustible;  when  incompletely  burnt  they  emit  a 
characteristic  odor  (acrolein).  When  kept  exposed  for  a long 
time,  they  become  rancid  (odor). 

10.  Before  the  war,  cotton  seed  was  a waste  product  in  our 
southern  states.  Now,  the  COTTON  SEED  OIL  adds  mate- 
rially to  the  profit  of  the  planter.  Enormous  quantities  are 
produced;  much  goes  to  the  packing  establishments  of  this 
country,  and  “over  six  million  gallons  are  shipped  annually  to 


260 


LECTURE  60. 


Mediterranean  ports  contiguous  to  the  olive  oil  industry” 
(Remington).  Alcoholic  silver  nitrate  solution,  shaken  with 
cotton  seed  oil,  and  heated,  tinges  the  oil  red  or  reddish- 
brown. 

11.  The  fact  is,  lard  oil,  cotton  seed  oil  and  olive  oil 
consist  mainly  of  olein  and  margarin  in  similar  proportions. 
By  density  and  solidification  they  can  not  be  distinguished. 
It  is  true,  lard  oil  produces  a COLOR  REACTION  with  sul- 
phuric acid  and  cotton  seed  oil  another  with  silver  nitrate 
solution;  but  these  tests  indicate  the  presence  of  an  impurity 
that  may  be  removed.  Of  course,  good  cotton  seed  oil  is  a 
good  oil,  and  will  bring  a good  price  sold  under  its  own  name. 

12.  To  conclude  the  identity  of  these  oils  is  manifestly 
absurd.  The  constituents  present  in  minute  amount,  the 
combinations  breaking  down  before  our  reagents,  often  are  the 
most  valued,  to  say  nothing  of  the  history  or  provenance  of 
the  material.  The  “artificial  wine”  may  yield  the  same 
analytical  results  as  a true  wine;  yet  the  maker  of  the  first  is 
condemned  in  Germany,  where  the  latter  brings’ a high  price. 
Frauds  in  oils  and  fats  are  frauds;  where  chemistry  fails  to 
detect  it,  the  brand  of  an  honorable  firm  will  protect  the  con- 
sumer and  the  producer. 

60.  FLOWER  AND  FRAGRANCE. 

1.  Its  highest  form  of  beauty  and  fragrance,  the  vegetable 
world  has  produced  in  THE  ROSE.  Though  in  the  lower  sense 
“useless” — offering  nothing  for  the  stomach  — the  rose  has 
ever  been  held  in  the  highest  estimation  by  man.  Flundreds 
of  varieties  have  been  produced  by  culture;  but  the  old  centi- 
folia  and  damascena  are  among  the  richest  in  fragrance. 

2.  In  the  Orient,  the  culture  of  the  rose  has  remained 
economically  prominent  in  numerous  localities.  The  country 
about  Kisanlik,  in  Bulgaria,  largely  supplies  the  market  with 
the  OIL  OF  ROSE,  in  which  the  subtle  fragrance  is  concen- 
trated in  a permanent  form.  This  oil,  quoted  at  about  a dollar 


FLOWER  AND  FRAGRANCE. 


2G1 


a drachm,  represents  fully  three  thousand  times  its  own  weight 
of  the  delicate  rose  petals.  It  is  a pale,  yellowish,  transparent 
liquid  (G  about  0.87  at  20  degrees),  congealing  between  16 
and  21  degrees  to  a transparent  solid  with  many  slender, 
shining  crystals. 

3.  The  oil  of  rose  is  obtained  by  distilling  rose  petals  with 
water;  the  oil  floats  on  top  of  the  distillate.  VOLATILE  OILS, 
even  if  of  much  higher  boiling  point  than  water,  are  readily 
carried  over  with  the  large  excess  of  water  vapor  in  this  pro- 
cess of  distillation,  which  is  quite  generally  employed  for  the 
extraction  of  the  fragrant  principles  of  plants.  In  some  dis- 
tricts this  ATTAR  is  distilled  without  the  addition  of  water  to 
the  petals,  the  latter  containing  a sufficiency  for  the  purpose. 

4.  Many  of  the  most  beautiful  and  FRAGRANT  FLOWERS 
are  grown  on  a commercial  scale  in  favored  regions  in  the 
open,  and  throughout  the  civilized  world  under  glass,  to  supply 
the  demand  in  the  immediate  vicinity  for  the  flower.  Flori- 
culture has  enormously  increased  during  the  last  quarter 
century.  Florists  have  also  learned  to  ship  their  perishable 
products  long  distances,  as  from  Sicily  to  England. 

The  southeastern  corner  of  France,  with  Nice  as  the  com- 
mercial center,  is  the  most  remarkable  flower  garden  of 
modern  times.  The  country,  gently  sloping  towards  the 
sunny  Mediterranean,  is  completely  protected  by  the  Maritime 
Alps  against  the  chilling  winds  of  the  north.  From  this 
favored  region,  fresh  flowers  are  shipped  to  the  north — as  far 
as  England — during  the  winter,  and  the  fragrance  of  flowers 
is  extracted  on  a large  scale  throughout  the  year. 

5.  The  finest  and  most  delicate  fragrance  of  flowers  suffers 
to  an  appreciable  extent  by  the  process  of  distillation  with 
water.  For  such  flowers,  the  process  of  ENFLEURAGE  has 
been  devised,  in  which  the  purest  fats  (lard),  spread  in  thin 
layers  on  glass  frames,  absorb  the  fragrance  of  the  flowers  at 
common  temperatures.  The  flowers  are  laid  or  sprinkled  on 
these  “chassis,”  of  which  a number  are  piled  to  a stack.  In 
from  6 to  12  hours  the  fats  have  absorbed  all  the  fragrance ; 


262 


LECTURE  60. 


the  exhausted  flowers  are  removed  and  replaced  by  fresh  ones 
till  the  fat  is  saturated. 

6.  This  POMADE  is  the  commercially  permanent  form  in 
which  the  concentrated  fragrance  of  the  flower  is  shipped 
throughout  the  world.  The  largest  establishments  of  this 
manufacture  are  at  Grasse,  about  15  miles  west  of  Nice.  This 
industry  is  strongly  marked  by  peculiar  characters  for  which 
French  industry  is  noted.  In  a very  small  bulk,  an  immense 
amount  of  skilled  labor  and  scientific  thought  has  been  con- 
densed ; a very  small  weight  brings  the  producer  a very  large 
sum  of  money. 

7. -  The  receiver — retailer — of  these  pomades,  cuts  them 
into  small  pieces,  and  shakes  these  with  the  proper  amount 
of  purest  alcohol,  which  dissolves  the  fragrance,  forming  the 
so-called  ESSENCE  of  the  flower;  the  fat  being  insoluble  in 
alcohol,  is  removed  by  decantation  (best  after  standing  in  the 
cold) . It  is  only  when  properly  diluted  that  the  real  fragrance 
is  brought  out. 

8.  Algiers,  Australia  and  the  United  States  have  made  a 
good  start  in  this  interesting  and  profitable  field.  The  pepper- 
mint culture  and  industry  of  Michigan  has  attained  a control- 
ling influence  in  the  market.  The  OIL  OF  PEPPERMINT  is 
distilled  with  water  from  the  leaves  and  tops  of  Mentha 
piperita,  gathered  before  flowering.  The  oil  (G  0.91)  has 
“the  characteristic  odor  of  peppermint;  a strongly  aromatic, 
pungent  taste,  followed  by  a sensation  of  cold  when  air  is 
drawn  into  the  mouth.” 

9.  The  small  evergreen  shrub,  rising  at  intervals  from  the 
creeping  root  of  Gaultheria  procumbens  yields,  upon  the 
distillation  of  its  oval,  leathery  leaves,  the  OIL  OF  WINTER- 
GREEN,  the  heaviest  of  all  volatile  oils  (G  1.18,  B 218-221). 
It  is  colorless  or  yellowish,  and  has  a strong  specific  odor,  a 
warm  aromatic  taste ; it  is  soluble  in  alcohol;  when  shaken 
with  water,  a deep  violet  color  will  be  produced  upon  the 
addition  of  a drop  of  ferric  chloride. 


FLOWER  AND  FRAGRANCE. 


2G3 


10.  An  “artificial”  or  “synthetic”  oil  of  wintergreen 
has  been  put  on  the  market;  being  made  from  “synthetic” 
salicylic  acid,  obtained  from  coal  tar,  it  is  profitably  supplied 
at  half  the  price  of  the  genuine. 

The  “artificial”  is  in  no  sense  chemically  identical  with  the 
genuine;  it  is  not  even  a safe  “substitution.”  But  it  is  de- 
clared to  be  as  good  as  the  genuine,  and  that  it  has  driven  the 
genuine  out  of  the  market,  so  that  even  “salicylic  acid  made 
from  oil  of  wintergreen”  is  no  longer  genuine.  “If  cheaper 
and  better,”  it  ought  by  all  means  to  be  sold  under  its  own 
name.  Such  a condition  is  deplorable,  demoralizing.  It  can 
be  met  by  a reliable  “brand”  only.  See  59.12. 

11.  Several  volatile  oils  are  obtained  BY  EXPRESSION, 
notably  the  oils  of  bergamot,  of  orange  peel  and  of  lemon  peel. 
For  further  details,  special  treatises  must  be  consulted  about 
this  entire  subject. 

The  pure  volatile  oils  make  a STAIN  on  paper;  but  this 
stain  completely  disappears  on  exposure,  while  the  stain  made 
by  fatty  oils  is  permanent. 

12.  From  peppermint  oil  separates  a crystallized  solid*,  called 
MENTHOL  (G  — , F 43,  B 212),  volatilizing  considerably  at 
common  temperatures.  The  Japanese  oil  is  particularly  rich 
in  menthol,  which  first  reached  us  from  Japan. 

Camphor  (G  0.995,  F 175,  B 204),  distilled  with  water 
from  the  wood  of  the  camphor  tree  of  Formosa,  is  similar  to 
menthol,  but  has  been  long  in  use.  Its  odor  is  characteristic 
and  well  known. 


61.  INDIGO  AND  MADDER. 

1.  The  vegetable  world  presents  in  its  flowers  all  the 
colors  of  the  rainbow;  it  also  shows  rich  color  in  fruit  and  foli- 
age, and  even  in  wood  and  root.  Man  has  tried  to  extract  and 
employ  these  colors;  but  the  tints  of  the  petals  have  almost 
invariably  proved  too  dainty  for  his  hands.  From  the  other 


264 


LECTURE  61. 


parts  of  the  plant,  SUBSTANTIAL  COLORING  MATTERS  have 
been  obtained. 

2.  Already  in  antiquity,  these  colors  were  transferred  to  the 
vegetable  fibre  by  which  man  protected  and  adorned  his  body. 
The  oldest  part  of  the  Scriptures  speak  of  GARMENTS  DYED 
in  red,  purple  and  scarlet.  The  heros  of  Homer  wore  purple. 
The  dyers  of  Tyre  and  Sydon  were  famous.  The  Egyptians, 
as  Pliny  reports,  understood  the  use  of  mordants,  apparently  as 
well  as  we  do  to-day. 

3.  INDIGO  is  one  of  the  oldest  vegetable  colors;  it  has 
been  in  use  at  least  three  thousand  years,  and  is  as  important 
to-day,  as  ever.  Eight  thousand  tons  of  indigo,  worth  over 
twenty  million  dollars,  are  produced  annually,  mainly,  in  India, 
its  home,  whence  Alexander  brought  it  to  Greece  as  indian 
(indicon)  blue.  In  naming  the  substance  we  state  its  origin. 

4.  The  plant,  indigofera  tinctoria,  shows  no  blue  coloring 
material.  Shortly  before  flowering,  the  plant  is  cut  off,  thrown 
into  great  vats  with  water  and  lime;  a sort  of  fermentation 
sets  in,  the  coloring  material  passing  into  solution.  This 
greenish -yellow  solution  is  drawn  into  lower  vats,  beaten  with 
bamiboos  for  hours  to  introduce  air;  now  a blueish  sediment 
settles  to  the  bottom — it  is  the  CRUDE  INDIGO,  about  one 
fifth  of  one  per  cent  of  the  plant  taken. 

5.  The  crude  indigo  of  commerce  contains  several  coloring 
principles.  Its  percentage  of  true  indigo  is  extremely  variable, 
ranging  from  20  to  90.  The  deep  blue  lumps  show  a reddish 
streak.  PURE  INDIGO  is  obtained  by  mixing  the  pulverized 
crude  substance  with  its  weight  of  pulverized  glucose,  dissolv- 
ing in  alkaline  alcohol.  The  yellowish  solution  is  decanted; 
upon  exposure  to  the  air  indigo  gradually  precipitates,  and 
after  washing  with  dilute  muriatic  acid,  is  pure. 

6.  PURE  INDIGO  BLUE  is  a blue,  tasteless  (crystalline) 
solid,  insoluble  in  water,  alcohol,  ether,  acids  and  alkalies, 
slightly  soluble  in  chloroform,  glacial  acetic  acid  and  spirits  of 
turpentine,  from  which  solutions  it  separates  in  acicular  crys- 


INDIGO  AND  MADDER. 


2G5 


tals.  When  carefully  heated,  it  forms  a sublimate  of  red 
acicular  crystals;  its  vapors  are  purplish  red.  It  is  soluble  in 
fuming  sulphuric  (Nordhausen)  acid.  In  reducing  alkaline 
liquids  it  dissolves  to  a colorless  liquid,  indigo-white  (Chevreul, 
p.  37);  on  exposure  to  the  air  it  returns  to  indigo-blue  or 
true  indigo.  This  explains  the  common  method  of  dyeing 
with  indigo. 

7.  India  is  also  the  home  of  rubia  tinctorum  (MADDER), 
the  root  of  which  has  served  from  time  immemorial  as  the 
principal  red  dye.  From  the  Orient,  the  culture  of  madder 
reached  Europe  in  the  17th  century,  and  became  specially 
prominent  in  southern  France.  Since  1869,  this  old  industry 
has  almost  disappeared,  not  only  from  France,  but  also  from 
Asia  Minor  and  other  countries,  to  the  great  loss  of  the  popu- 
lations affected. 

8.  The  pulverized  madder,  treated  with  its  own  weight  of 
sulphuric  acid,  gives  a blood  red  mass,  the  garancine  of  the 
French.  Exhausting  this  with  boiling  alcohol,  the  cooling 
liquid  deposits  yellowish  brown  acicular  crystals  of  ALIZARINE 
and  purpurine.  Both  are  soluble  in  a boiling  solution  of  alum, 
from  which  alizarine  precipitates  on  cooling.  This  is  the  color- 
ing principle  of  madder. 

9.  The  reddish  yellow  crystals  of  PURE  ALIZARINE  melt  at 
215°,  volatilize  between  this  temperature  and  240°;  they  can 
be  sublimated  in  a porcelain  crucible  heated  on  a sandbath. 
Alizarine  is  scarcely  soluble  in  water,  moderately  soluble  in 
boiling  water  and  in  alcohol.  It  dissolves  in  sulphuric  acid, 
which  it  colors  blood  red.  Its  alcoholic  solution  is  turned  violet 
by  alkalies;  lime  turns  it  blue.  A hot  alum  solution  dis- 
solves it;  on  cooling,  it  precipitates  in  crystal  form. 

10.  In  1869  the  German  Chemists,  Graebe  and  Lieber- 
mann,  succeeded  in  producing  alizarine  from  anthracene,  one 
of  the  least  volatile  constituents  of  coal  tar.  Their  method 
was  unpracticable,  however.  The  English  Chemists,  Caro 
and  Perkin,  soon  after,  devised  a chemical  method  both  simple 


26G 


LECTURE  62. 


profitable.  Since  then,  ALIZARINE  IS  MADE  on  a large  scale 
FROM  COAL  TAR,  and  the  madder  culture  has  been  ruined. 
France  used  to  export  six  million  dollars  worth  of  madder;  now 
Germany  produces  that  much  alizarine  from  coal  tar. 

11.  The  two  vegetable  colors  presented  are  TYPICAL  of 
this  important  class  of  bodies.  Many  lessons,  economic  as 
well  as  scientific,  can  be  drawn  from  what  has  been  stated. 

In  conclusion,  the  economic  value  of  colors  extracted  from 
woods  (logwood,  etc.),  may  be  estimated  from  the  fact  that 
Europe,  in  1888,  imported  two  hundred  thousand  tons  of  such 
woods  from  the  tropics,  representing  about  eight  million  dollars 
in  value. 

12.  The  most  important  vegetable  color  of  all  has  not  been 
mentioned  yet;  it  is  CHLOROPHYLL,  the  green  color  of 
leaves.  It  is  insoluble  in  water,  but  soluble  in  alcohol,  and 
especially  in  ether.  By  frost  it  is  decomposed  into  red  and 
yellowish  tints,  so  admirably  exhibited  by  American  forests  in 
the  fall  season.  In  spring,  more  delicate  tints  mark  the  swell- 
ing and  opening  buds— but  require  more  attention  to  be  seen. 


62.  BALSAM  AND  RESIN. 

1.  We  read  of  “wise  men  from  the  East”  having  been 
miraculously  guided  by  a star  to  the  new-born  King;  “and 
when  they  had  opened  their  treasures,  they  presented  to  him 
gifts:  gold,  and  frankincense,  and  myrrh.”  This  is  a formal 
recognition  of  the  estimation  in  which  Orientals  hold  choice 
resins  and  balsams — treasured  with  gold. 

2.  Modern  man  looks  down  upon  such  customs  as  manifes- 
tations of  ignorance  and  superstition— and  then  dives  into  the 
TAR  PIT,  applies  all  his  powers  and  extracts  by  highest 
chemical  art  “new”  substances  of  wonderful  properties,  makes 
the  use  of  these  products  almost  compulsory  to  cure  and  pre- 
vent disease,  and  to  preserve  food  from  corruption  ’till  needed 
for  strength. 


BALSAM  AND  RESIN. 


2G7 


3.  And  lo!  these  vaunted  NEW  SUBSTANCES  owe  their 
value  exclusively  to  their  correspondence  with  the  exudations 
of  the  fragrant  shrubs  and  trees  of  India,  Arabia  and  Africa, 
used  and  prized  from  time  immemorial  by  our  superstitious 
ancestors  who,  however,  were  not  ignorant  enough,  by  such 
substances,  to  make  their  food  indigestible.  The  Egyptians 
preserved  their  lifeless  bodies,  but  they  did  not  embalm  their 
food. 

4.  BENZOIN  is  a balsamic  resin,  obtained  from  Styrax  Ben- 
zoin, a tree  at  home  on  Sumatra  and  Java.  Alcohol  dissolves 
most  of  its  active  principles.  When  moderately  heated,  it 
yields  a crystallized  aromatic  sublimate,  insoluble  in  water, 
but  soluble  in  sodium  carbonate  with  effervescence,  and  re- 
precipitated  by  sulphuric  acid.  The  sublimate,  accordingly,  is 
a true  acid;  it  is  called  benzoic  acid. 

5.  Scheele  (p.  169)  made  use  of  the  wet  way  reactions  just 
stated  to  extract  pure  benzoic  acid  from  benzoin. 

When  the  acid  is  heated  in  a distilling  apparatus  with  three 
times  its  weight  of  slacked  lime,  a colorless  distillate  is  ob- 
tained, called  BENZOL  (Mitscherlich,  p.  34).  This  sub- 
stance is  the  starting  point  of  all  aromatic  compounds.  We 
give  the  characteristic  of  these  two  bodies. 

6.  BENZOL  is  a colorless,  very  limpid  liquid  of  a character- 
istic odor.  G 0.90  at  0,  F 0°,  B 80.4;  crystallizes  in  rhom- 
bic octahedr^.  Insoluble  in  water,  soluble  in  alcohol  and 
ether.  Is  a good  solvent  for  iodine,  sulphur,  phosphorus, 
camphor,  wax,  fats,  and  india  rubber.  It  burns  with  a 
fuliginous  flame. 

7.  BENZOIC  ACID  (Equivalent  122)  is  a white  solid, 
forming  pearly  scales  or  silky  needles;  has  a slight  aromatic 
odor  of  benzoin,  and  a warm,  acid  taste;  acid  reaction.  F 121, 
B 250. , Very  slightly  soluble  in  cold  water  ( rJir)  moderately 
soluble  in  boiling  water  (t\),  quite  soluble  in  alcohol,  ether, 
chloroform,  benzol.  Freely  soluble  in  aqueous  solutions  of 
alkalies,  forming  soluble  salts. 


268 


LECTURE  62. 


It  begins  to  sublimate  at  100°  already,  and  freely  passes  over 
with  vapor  of  water.  Neutralized  solutions  give  a flesh 
colored  precipitate  with  ferric  chloride. 

8.  We  have  no  balsam  trees  in  the  North,  but  possess  im- 
mense pine  forests  which  impregnate  the  air  with  their 
peculiar  aroma — both  healthful  and  pleasant.  The  wood  is 
rich  in  an  oleoresin  (TURPENTINE),  to  obtain  which  the 
great  pine  forests  of  our  Southern  States  are  now  being 
devastated  by  “turpentine  orchards.”  The  turpentine  industry 
is  old  in  the  Carolinas.  Southwestern  France  also  produces 
turpentine,  but  not  in  that  ruthless  manner. 

9.  When  turpentine  is  distilled  with  water,  OIL  OF 
TURPENTINE  forms  a layer  on  the  water  passing  over.  The 
volatile  oil  may  be  rectified  from  lime  water. 

Oil  of  turpentine  is  a thin,  limpid,  very  volatile,  colorless 
liquid,  of  a characteristic  odor  and  taste,  neutral  reaction  (be- 
coming faintly  acid  by  exposure  to  the  air).  G.  0.86  to  0.87. 
Insoluble  in  water,  soluble  in  thrice  its  volume  of  alcohol.  It 
acts  on  bromine  or  iodine  with  explosive  violence;  in  contact 
with  a mixture  of  nitric  and  sulphuric  acid,  it  inflames.  Its 
vapors  mixed  with  air  explode  on  ignition. 

10.  The  residue  left  of  the  turpentine  after  distilling  is 
called  colophony.  It  is  a true  resin,  being  readily  soluble  in 
alcohol,  and  entirely  insoluble  in  water. 

COLOPHONY  is  a transparent,  amber  colored  solid,  hard, 
brittle,  with  conchoidal  fracture,  showing  the  typical  resinous 
luster;  it  has  a faint  terebinthine  odor,  and  is  inflammable. 
G 1.07  to  1.08,  F 135.  Solubility  as  stated  above;  also 
readily  soluble  in  ether,  fixed  and  volatile  oils. 

11.  Oil  of  turpentine,  when  distilled  in  vacuo  or  in  an 
atmosphere  of  fixed  air,  is  destitute  of  odor.  Exposure  to  the 
air  reproduces  the  odor,  which  accordingly  is  due  to  the  oxida- 
tion of  the  oil,  which  thereby  is  resinified.  All  volatile  oils 
seem  to  possess  this  peculiarity.  In  the  same  manner,  pure 
arsenic  distilled  in  fixed  air  has  no  odor;  it  exhibits  the 
characteristic  garlic  ODOR  ONLY  WHILE  BEING  OXIDIZED. 


BALSAM  AND  RESIN. 


269 


12.  Turpentine  yields  about  one  fifth  of  its  own  weight  of 
volatile  oil,  leaving  four  fifths  of  resin.  Such  bodies  are 
named  OLEO-RESINS.  GUM  RESINS  consist  of  a gum  (soluble 
in  water,  insoluble  in  alcohol)  and  a resin.  Myrrh  and  asa- 
foetida  are  examples.  Balsams  are  resinous  substances  con- 
taining benzoic  acid  or  similar  aromatic  volatile  solids.  Styrax, 
balsam  of  Tolu,  balsam  of  Peru,  may  be  mentioned  in  addi- 
tion to  benzoin  described. 


63.  VEGETABLE  ACIDS. 

1.  Goethe  voiced  the  longing  of  the  children  of  the  North 
for  the  “ Sunny  South,”  the  land  where  the  lemon  trees  are 
in  bloom,  and  where  through  the  dark  foliage  the  golden 
ORANGES  glow.  Nevertheless,  the  Northern  APPLE  orchard 
in  full  blossom  at  the  coming  of  the  summer  season,  and 
loaded  with  luscious  fruit  at  its  close,  we  deem  the  more 
beautiful  of  the  two.  It  was  an  apple,  not  an  orange,  that 
tempted  the  mother  of  us  all. 

2.  Chemically,  both  the  lemon  and  the  apple  furnish  us 
typical  ORGANIC  ACIDS,  namely  citric  and  malic  acids. 
SCHEELE,  that  marvellously  skillful  chemical  worker,  has 
taught  us  how  to  extract  these  acids.  Though  a century  has 
elapsed,  we  cannot  do  better  than  follow  his  directions  (p.  169). 

3.  While  climatic  conditions  limit  the  habitat  of  the  trees 
producing  these  REFRESHING  FRUITS,  the  almost  ripe  fruit  is 
sufficiently  resistant  to  stand  shipment  to  distant  countries. 
Thus  Italy  and  California  supply  the  world  with  lemons  and 
oranges,  while  our  Northern  States  send  apples  to  Europe  by 
the  million  barrels. 

4.  THE  JUICE  OF  THE  LIME  contains  more  citric  acid  than 
the  lemon  and  largely  supplies  the  growing  demand  for  this 
acid.  After  freeing  the  juice  from  mucilage  by  a beginning 
fermentation,  it  is  saturated  with  chalk,  the  precipitated 


270 


LECTURE  63. 


calcium  citrate  washed  with  boiling  water  and  treated  with 
dilute  sulphuric  acid.  The  resulting  citric  acid  solution  is 
drawn  off  from  the  precipitated  gypsum  and  concentrated  to 
crystallization. 

5.  CITRIC  ACID  occurs  in  colorless,  translucent,  right- 
rhombic  prisms,  not  deliquescent  in  dry  air;  odorless,  agreeable 
acid  taste.  Freely  soluble  in  water,  less  so  in  alcohol.  It  gives 
no  precipitate  with  lime  water  except  on  boiling;  the  precipitate 
redissolves  on  cooling  (if  an  excess  of  lime  water  was  used). 

The  crystallized  acid  (equivalent  70)  begins  to  lose  water 
(of  crystallization)  at  about  75;  melts  above  135,  and  decom- 
poses at  a red  heat,  without  emitting  the  odor  of  burnt  sugar. 

6.  The  acid  which  Scheele  in  1785  extracted  from  the  apple 
(pyrus  malus)  he  called  MALIC  ACID.  He  found  the  same 
acid  in  cherries,  currants,  blackberries,  strawberries  and 
other  fruit.  The  barberries,  the  berries  of  sumac  (rhus  glabra) 
and  of  the  european  mountain  ash  are  especially  rich  in  this 
acid.  It  also  occurs  in  rhubarb  and  tobacco. 

7.  These  berries  of  the  mountain  ash  are  gathered  before 
they  are  fully  ripe.  The  juice  is  expressed,  and  clarified  by  being 
brought  to  a boiling  (albumin).  The  filtered  liquid  is  boiled 
with  milk  of  lime,  giving  a deposit  of  neutral  calcium  malate. 
After  washing,  this  deposit  is  added,  in  small  portions  at  a 
time,  to  boiling  dilute  nitric  acid;  the  acid  malate  so  formed 
crystallizes  on  cooling.  These  crystals  are  treated  with  lead 
acetate,  the  lead  malate  precipitated  is  suspended  in  water 
and  treated  with  hydrogen  sulphide  gas.  The  filtrate  yields, 
on  careful  evaporation,  deliquescent  crystals  of  malic  acid. 

8.  Malic  acid  (equivalent  67)  occurs  in  acicular  crystals, 
forming  mamellary  groups;  it  is  deliquescent,  very  soluble  in 
water  and  in  alcohol.  F 100.  It  begins  to  decompose  at 
120  degrees. 

Malic  acid  gives  no  precipitate  with  lime  water,  neither  hot 
nor  cold.  Calcium  chloride  gives  no  precipitate,  except  upon 
boiling.  This  precipitate,  dissolved  in  the  least  amount  of 
hydrochloric  acid,  is  reprecipitated  by  alcohol. 


VEGETABLE  ACIDS. 


271 


9.  Scheele  separated  several  other  organic  acids  by  his 
methods,  namely:  the  formation  of  the  calcium  salt  from  which 
the  organic  acid  is  set  free  by  dilute  sulphuric  acid  under  the 
separation  of  insoluble  gypsum,  or  the  formation  of  the  lead 
salt,  from  which  the  lead  is  separated  by  hydrogen  sulphide. 
In  addition  to  the  preceding  acids,  he  extracted  especially 
oxalic  and  tartaric  acids  in  this  way. 

10.  OXALIC  ACID  is  extracted  from  various  species  of  sorrel 
(oxalis),  generally  containing  the  potassium  salt.  The  acid 
is  now  made  in  quantity  from  starch  or  from  sawdust. 

Crystallized  oxalic  acid  (equivalent  63)  is  quite  permanent 
in  air  (24.10)  and  moderately  soluble  in  water.  Calcium 
compounds  give  a crystalline  precipitate,  insoluble  in  acetic  or 
oxalic  acid,  but  soluble  in  muriatic  acid.  See  p.  146,  5,  a ; 55,9. 

11.  Potassium  tartrate  is  contained  in  the  ripe  grape,  and 
insoluble  in  alcohol ; it  therefore  separates  as  tartar  (argol) 
during  fermentation.  This  is  dissolved  in  dilute  muriatic 
acid,  and  saturated  with  chalk.  The  precipitated  neutral 
calcium  tartrate  is  washed  and  treated  with  dilute  sulphuric 
acid;  the  filtrate  is  carefully  evaporated  (best  in  vacuum  pan) 
to  crystallization. 

12.  TARTARIC  ACID  (equivalent  75)  forms  colorless,  odor- 
less, monoclinic  crystals,  permanent  in  air.  F 135,  decompose  at 
higher  temperature,  emitting  the  odor  of  burnt  sugar.  Soluble 
in  water,  less  so  in  alcohol. 

The  acid  gives  a crystalline  precipitate  (cream  of  tartar) 
with  potassium  acetate,  insoluble  in  acetic  acid,  readily  soluble 
in  alkalies  and  in  mineral  acids. 


64.  VEGETABLE  BASES. 

1.  The  strange  potency  of  many  plants  had  become  familiar 
to  man  long  before  historic  times.  The  myths  of  Hekate, 
daughter  of  night,  and  of  her  high  walled  garden  full  of 
POISONOUS  PLANTS,  are  sufficient  evidence.  Concordant 


272 


LECTURE  64. 


herewith,  modern  explorers  have  found  most  savage  races  in 
possession  of  poisons  and  narcotic  remedies. 

2.  Even  the  SPECIFIC  ACTION  OF  POISONS  was  known 
to  the  ancients,  partly  studied  by  experiments  on  condemned 
criminals  or  slaves.  The  most  famous  instance  of  this  knowl- 
edge we  read  in  Plato’s  account  of  the  tests  made  by  the  exe- 
cutioner on  Socrates,  verifying  his  prediction  of  the  action  of 
the  fatal  cup  by  which  the  civilized  Greeks  relieved  them- 
selves of  their  greatest  teacher. 

3.  Besides,  most  races  of  men  have  become  addicted  to  the 
use  of  some  potent  plant  as  STIMULANT  OR  NARCOTIC. 
Poppy  in  the  eastern  hemisphere.  Tobacco  in  the  western 
world.  Tea  in  China,  Coca  in  South  America;  Coffee  in 
Abyssinia,  Chocolate  in  Mexico.  The  pure  wines  of  the 
Ancients  of  our  own  race  have  been  fortified  in  the  destructive 
spirits  manufactured  by  their  descendants. 

4.  The  dominant  race,  in  its  conquest  of  the  continents  of 
the  West  and  South,  PAYS  TRIBUTE  to  China  for  tea,  to 
America  for  tobacco,  and  has  planted  the  coffee  tree  wherever 
it  will  grow.  The  cultivation,  transportation  and  distribution 
of  these  apparently  useless  plants  has  become  an  important 
factor  in  the  economy  of  nations.  In  reality  they  must  supply 
a legitimate  want. 

5.  The  remarkable  action  on  the  system,  depending  in  its 
character  on  the  amount  taken,  has  always  been  well  known, 
but  too  often  disregarded.  In  MINUTE  DOSES,  strychnine  is 
a valuable  remedy,  but  already  half  a grain  may  kill  under 
horrible  convulsions.  Opium,  in  small  doses,  relieves  the 
sick  of  pain ; habituation  to  larger  doses,  stupefies  the  mind 
and  kills  the  body.  These  substances  evidently  are  like 
knives  and  guns,  requiring  skill  and  understanding  for  their 
proper  use. 

6.  Many  of  these  active  vegetable  materials  have  never 
been  employed  except  as  remedies.  The  bark  of  the  CIN- 
CHONA trees  of  the  Andes  were  so  used  against  fevers  by  the 


VEGETABLE  BASES. 


273 


natives,  who  imparted  this  knowledge  to  their  conquerors. 
The  process  of  gathering  the  bark  (p.  52)  being  destructive, 
cinchona  plantations  have  been  established  in  the  Dutch  and 
English  colonies  of  India.  Rational  cultivation  and  harvest 
now  supply  the  valued  bark  at  reasonable  rates. 

7.  Until  1817  the  active  principles  of  these  remarkable 
substances  remained  unknown.  FREDERICK  SERTUERNER, 
a pharmacist  of  northwestern  Germany,  had  already  in  1805 
separated  the  “principium  somniferum”  of  opium,  the  inspiss- 
ated juice  of  the  poppy,  and  also  extracted,  by  Scheele’s  pro- 
cess, meconic  acid  from  the  drug.  But  hardly  any  attention 
was  paid  to  his  results  ’till  in  1817,  he  published  his  method 
of  extracting  morphine  from  opium. 

8.  Sertuerner  treated  opium  with  dilute  acetic  acid,  precip- 
itated the  filtered  solution  with  ammonia,  and  purified  the  pre- 
cipitate by  crystallizing  it  from  its  solution  in  hot  alcohol;  this 
substance  he  called  MORPHINE.  It  forms  white,  slender  pris- 
matic crystals,  permanent  in  air,  very  bitter;  scarcely  soluble 
in  water,  ether  or  benzol,  moderately  soluble  in  alcohol, 
especially  when  warm,  and  readily  soluble  in  purified  fusel  oil. 

Morphine  crystals  are  identified  by  turning  orange  red  with 
nitric  acid,  and  blue  with  neutral  ferric  chloride. 

9.  THIS  MODE  OF  EXTRACTION  proves  morphine  to  be 
a base,  brought  into  solution  by  acetic  acid,  and  precipitated 
by  ammonia  because  it  is  insoluble  in  water.  With  acids  it 
forms  definite  salts,  generally  soluble  in  water,  from  which 
they  can  be  obtained  in  crystal  form.  They  are  insoluble  in 
most  organic  solvents.  Resembling  the  alkalies,  morphine  is 
called  an  alkaloid. 

10.  Nearly  all  the  plants  referred  to  above  contain  active 
principles  of  this  kind,  or  ALKALOIDS.  They  are  EXTRACTED 
from  the  crude  drug  by  a like  process,  modified  according  to 
the  special  solubility  of  the  alkaloids;  they  are  distinguished 
or  IDENTIFIED  most  generally  by  some  specific  color  reaction. 
This  important  subject  can  hardly  be  studied  with  profit  ex- 
cept in  the  laboratory  course. 


274 


LECTURE  G5. 


11.  Nux  vomica  contains  the  alkaloid  STRYCHNINE,  very 
soluble  in  chloroform.  It  is  identified  by  remaining  white 
(colorless)  with  concentrated  sulphuric  acid,  and  striking  a 
deep  blue  color  with  a crystal  of  potassium  bichromate,  drawn 
through  the  acid  film  covering  the  strychnine  crystals.  This 
blue  color  almost  instantly  changes  to  deep  blueish  violet, 
which  gradually  passes  into  an  indefinite  reddish  tint.  See  59,  7. 

12.  The  ALKALOIDS  of  tobacco  (nicotine)  and  of  hemlock 
or  conium  maculatum  (coniine)  are  VOLATILE  liquids;  hence 
they  can  be  obtained  by  distilling  the  drug  with  dilute  potass- 
ium hydrate.  The  impure  distillate,  made  alkaline  with  po- 
tassium hydrate  and  shaken  with  ether,  will  yield  the  alkaloid 
on  spontaneous  evaporation  of  the  ethereal  solution.  Coniine 
is  distinguished  by  its  strong,  mousy  odor.  Hemlock  infusion 
was  the  poison  cup  of  the  Greeks;  see  2. 


65.  NEUTRAL  PRINCIPLES. 

1.  ' Many  plants  yield  to  neutral  solvents,  such  as  water 
and  alcohol,  crystalline  substances  destitute  of  marked  acid 
or  alkaline  properties;  such  substances  are  called  neutral 
principles.  Some  of  these  principles  resemble  alkaloids,  others 
seem  to  act  like  acids.  Most  have  a marked  taste,  especially 
bitter  or  astringent,  and  some  act  powerfully  on  the  system 
(cathartics). 

2.  THE  BARK  OF  THE  WILLOW  imparts  an  intense  red 
color  to  sulphuric  acid.  Poured  into  water,  the  diluted  acid 
gradually  becomes  colorless,  depositing  a dark  red  precipitate. 
These  reactions  are  due  to  salicin,  which  may  be  extracted  by 
boiling  the  bark  with  milk  of  lime,  evaporating  the  clear, 
decanted  solution  to  dryness,  and  exhausting  the  residue  with 
weak  alcohol ; the  salicin  will  crystallize  after  the  alcohol  has 
been  distilled  off. 


NEUTRAL  PRINCIPLES. 


3.  SALICIN  crystallizes  on  cooling  from  hot  solutions  in 
water  or  in  alcohol,  forming  white,  silky  needles,  permanent 
in  the  air;  it  is  odorless,  very  bitter;  its  solutions  have  a 
neutral  reaction.  F 198.  It  has  been  used  as  a febrifuge. 

It  is  identified  by  the  above  given  reaction  with  sulphuric 
acid  and  water.  Heating  a small  portion  with  the  chromic 
oxidizing  mixture  (bichromate  and  sulphuric  acid),  the  char- 
acteristic odor  of  the  oil  of  meadow  sweet  (spiraea  ul maria) 
will  be  noticed. 

4.  When  salicin  is  boiled  with  dilute  sulphuric  acid,  the 
solution  will,  after  neutralization,  give  the  glucose  reaction 
with  Fehlings  reagent  (58.7);  accordingly,  glucose  has  been 
formed  from  salicin.  Special  researches  have  shown  that 
there  also  forms  the  compound,  saligenin,  and  that  water 
has  been  taken  up.  Substances  which  take  up  water  and 
yield  glucose,  are  called  GLUCOSIDES. 

5.  The  flower  heads  of  Artemisia  paucitlora  are  sold  under 
the  name  of  Santonica  (Levant  Wormseed).  Mixing  the 
ground  “wormseed”  with  slacked  lime,  and  exhausting  the 
mixture  with  hot  water,  the  concentrated  filtrate  yields  crude 
SANTONIN  as  precipitate  on  the  addition  of  muriatic  acid. 
The  product  may  readily  be  purified  and  crystallized  from 
alcohol.  It  turns  yellow  by  exposure  to  light.  It  acts  like  a 
feeble  acid.  It  is  a noted  anthelmintic. 

6.  The  kernel  of  Cocculus  Indicus  is  bruised  and  extracted 
with  hot  alcohol ; this  solution  is  concentrated  to  a thick, 
syrupy  consistence  (removing  separated  fat).  Boil  the 
residue  with  water,  filter,  and  set  the  hot  filtrate  aside  for 
crystallization.  The  crude  crystals,  purified  by  recrystalliza- 
tion from  alcohol,  are  PICROTOXIN.  It  is  a bitter  glucoside, 
extremely  poisonous. 

7.  The  inspissated  juice  of  the  leaves  of  several  varieties 
of  Aloes  are  quoted  in  the  drug  market  under  the  name  of 
Gum  Aloes.  When  Barbadoes  aloes  is  treated  with  ten  times 


276 


LECTURE  65. 


its  own  weight  of  water  (slightly  acidified  with  muriatic  acid), 
the  liquid  decanted  after  cooling,  and  evaporated  to  about 
double  the  weight  of  the  gum  taken,  crystals  will  slowly  form 
(in  a week  or  two).  This  is  ALOIN  (barbaloin).  It  is 
extremely  bitter;  in  small  doses  (2  cgr)  a laxative,  in  larger 
doses  (10  cgr)  a cathartic. 

8.  The  inner  bark  of  Quillaja  Saponaria  of  South  America 
contains  the  glucoside  SAPONIN,  which  is  extracted  by  hot 
water.  Its  aqueous  solution  froths  when  agitated,  like  soap- 
suds; the  froth  is  very  slow  to  settle.  Medicinally  it  is  an 
irritant  diuretic;  technically  it  is  used  to  cleanse  silk.  It  is 
also  used  as  an  adulterant  to  foaming  liquids. 

9.  THE  TANNING  OF  HIDES  to  form  leather  is  one  of  the 
oldest  industries.  The  cleaned  animal  hide  decays  (putrefies) 
rapidly;  but  if  packed  in  white  oak  bark,  it  slowly  changes  to 
leather,  which  is  quite  permanent  in  both  air  and  water. 

The  active  principle  of  the  oak  bark  is  called  tannin.  It  is 
best  extracted  from  nut  galls,  which  contain  fully  half  their 
own  weight  of  tannin. 

10.  Powdered  NUT  GALLS  are  extracted  in  various  ways 
with  water  and  ether;  the  water  dissolving  the  tannin,  the 
ether  taking  up  the  impurities  from  the  solution.  The  liquids 
are  separated,  the  aqueous  solution  concentrated  and  spread 
to  dry  on  glass  or  tin  plates  to  obtain  the  TANNIN  as  a yellow- 
ish, non-crystallizable  powder.  It  is  very  soluble  in  water  and 
dilute  alcohol,  but  almost  insoluble  in  absolute  ether. 

11.  The  taste  of  tannin  is  strongly  astringent.  Its  solution 
precipitates  most  solutions  of  animal  materials,  especially 
gelatin  and  albumin;  hence  its  use  in  tanning.  It  also  pre- 
cipitates most  salt  solutions,  and  forms  with  ferric  solutions  a 
black  precipitate;  ferrous  solutions  turn  black  on  exposure  to 
air  (ink).  Tannin  acts  like  a feeble  acid,  but  has  been 
generally  considered  a glucoside. 

12.  Aqueous  solutions  of  tannin,  exposed  to  the  air,  undergo 
GALLIC  FERMENTATION,  due  to  the  presence  of  the  complex 


NEUTRAL  PRINCIPLES. 


277 


ferment  penicillium  glaucum.  Glucosides  present  yield  glu- 
cose which,  after  the  gallic  fermentation  is  completed,  give 
alcohol. 

Tannin  is  one  of  the  most  common  vegetable  products, 
contained  in  most  barks  and  leaves.  It  is  recognized  by  its 
astringent  taste  and  its  reaction  with  ferric  solutions  or  with 
gelatin. 


66.  STARCH  AND  FIBER. 

1.  Thus  far  we  have  by  the  simplest  methods  possible  ex- 
tracted our  organic  prime  materials  from  plants,  especially  by 
pressure,  heat  and  solvents.  The  insoluble  residue  left  in  all 
these  cases  constitutes  the  main  body  of  the  plant.  This  re- 
sistant material  gives  each  plant  its  characteristic  form.  It  is 
called  woody  fiber  or  CELLULOSE. 

2.  The  microscope  shows  the  wood  cell  to  be  essentially 
cylindrical  in  form,  varying  greatly  for  different  tissues  in  the 
same  pknt  and  for  corresponding  tissues  in  different  plants. 
By  treating  the  crushed  and  broken  tissue  in  succession  with 
the  solvents  used  to  extract  the  vegetable  principles  studied, 
the  WOODY  FIBER  will  remain  as  a white,  fibrous  mass, 
insoluble  in  water,  alcohol,  ether,  dilute  alkali  and  acid. 

3.  This  woody  fiber  may  be  extracted  from  almost  any 
plant  with  more  or  less  labor;  we  find  it,  however,  quite 
pure  in  COTTON,  the  fiber  of  which,  under  the  microscope, 
appears  as  twisted  ribbons.  The  so-called  absorbent  cotton 
is  obtained  by  removing  the  small  amount  of  fatty  material 
present  in  raw  cotton.  Linen,  the  smooth,  round  fiber  of  flax, 
is  also  very  pure  cellulose. 

4.  In  wood  proper,  the  true  cellulose  is  thickened  with 
LIGNIN,  which  is  brittle.  It  can  be  removed  by  treating  the 
properly  divided  wood  with  lime  saturated  with  sulphur  dioxide 
under  pressure  (2  to  3 atmospheres).  This  givesthe  WOOD- 


278 


LECTURE  66. 


PULP,  so  much  used  for  lower  grades  of  paper,  and  largely 
imported  from  Norway  and  Germany.  Phloroglucin  and  con- 
centrated muriatic  acid  turn  lignin  intensely  purple-red;  hence 
white  paper  can  be  tested  for  lignin  by  this  reagent. 

5.  Cellulose  can  be  dissolved  by  Schweizer’s  reagent;  an 
ammonical  solution  of  cupric  hydrate.  Cellulose  is  re-precipi- 
tated  by  acids,  forming  a white  amorphous  powder,  purified  by 
washing  with  alcohol. 

Some  animals  (Ascidia)  contain  a corresponding  material 
Tunicin  (animal  cellulose) ; in  its  solubilities  it  closely 
resembles  true  cellulose. 

6.  THE  IMPORTANCE  OF  CELLULOSE  TO  MAN  can 
hardly  be  expressed  in  words.  Man  has  dressed  himself  in 
linen  and  cotton ; coarser  fibers  he  uses  for  sacks  and  cordage. 
When  these  are  worn  out — rags — he  makes  paper  thereof. 
Of  the  wood  itself  he  builds  houses  and  ships,  and  also  burns 
it  for  comfort  and  power.  But  above  all,  woody  fiber  gives 
form  to  plants — the  beautiful  mantle  of  the  globe. 

7.  If  we  examine  a thin  slice  of  almost  any  tuber  or  seed, 
we  find  the  cells  of  the  tissue  to  contain  smaller  globular 
cells,  called  STARCH.  If  the  ground  or  crushed  material  is 
washed  on  a sieve  or  straining  cloth,  the  starch  runs  through 
the  cloth  with  the  water,  and  gradually  settles  in  the  receiv- 
ing vessels. 

8.  STARCH  GRAINS  show  concentric  layers  around  a 
nucleus  (hilum)  in  the  center  or  near  one  end  of  the  grain. 
The  form,  while  in  the  main  globular,  shows  specific  modifi- 
cations for  each  plant,  as  well  as  characteristic  dimensions,  so 
much  so  that  in  many  cases  the  plant  can  be  named  from  a 
microscopic  examination  of  the  starch. 

9.  POTATO  starch  is  the  largest  (60  to  100  microns), 
somewhat  egg-shaped,  the  excentric  hilum  and  rings  readily 
distinguished.  RICE  starch  is  among  the  smallest  (3  to  7 
microns),  the  grains  showing  polygonal  forms.  WHEAT  starch 


STARCH  AND  FIBER. 


279 


(20  to  30  microns),  is  larger  than  CORN  starch  (15  to  20 
microns)  ; the  former  is  spherical,  the  latter  somewhat  poly- 
hedral. A micron  is  the  thousandth  part  of  a millimeter;  it 
is  the  unit  of  microscopic  measures.  2,  5. 

10.  STARCH  is  insoluble  in  (cold)  water,  but  soluble  in 
strong  solutions  of  zinc  chloride,  calcium  chloride  and  similar 
salts.  Starch  is  also  insoluble  in  alcohol. 

When  starch  is  heated  with  water,  the  grains  swell  and 
burst,  giving,  on  boiling,  starch  paste.  Alcohol  precipitates 
herefrom  soluble  starch  as  a white  powder,  soluble  in  cold 
water.  In  the  paste,  the  membranes  remain  as  shreds;  the 
cell-contents  (granulose  or  amidin)  only  has  dissolved.  Iodine 
is  a most  delicate  reagent  for  starch  (23.4). 

11.  Starch,  being  one  of  the  principal  constituents  of 
FLOUR,  is  a valuable  food.  The  roller  process — like  the  mill 
stones  of  the  ancients — crushes  the  grain  without  tearing  it; 
but  excessive  bolting  produces  a very  white,  insipid  flour  con- 
taining an  undue  proportion  of  starch.  Potatoes  are  the 
poorest,  wheat  is  the  most  nutritive;  corn  contains  most  fat, 
rice  the  least  of  fiber. 

12.  STARCH  being  required  in  many  industries  (textile, 
paper,  glucose)  it  IS  MANUFACTURED  in  enormous  quantities. 
In  Germany  starch  is  largely  extracted  from  potatoes;  in  Rus- 
sia, from  wheat;  in  the  United  States,  from  corn  (maize),  and 
in  England  from  (imported)  rice.  From  the  tropics  we  get 
arrow- root  and  genuine  sago,  which  resembles  potato  starch 
somewhat;  accordingly  the  tuber  sometimes  is  sold  where  the 
palm  is  called  and  paid  for. 


67,  MILK  AND  BUTTER. 

1.  Milk  is  the  food  of  all  young  mammals;  to  man  it  is  a 
valuable  food  throughout  his  entire  existence.  The  most 
abundant  and  cheapest  source  is  THE  COW  (p.  49) ; the  best 
product  is  obtained  from  cows  in  good  pasture.  “The  old 


280 


LECTURE  67. 


pastures”  on  which  no  plow  has  drawn  furrow  for  centuries, 
extending  on  the  west  coasts  of  Germany  from  Holland  to 
Sleswig,  and  protected  by  dykes  from  the  sea,  furnish  milk  in 
flavor  and  richness  unsurpassed. 

2.  THE  PRODUCTION  OF  MILK  occupies  a prominent 
place  in  the  economy  of  nations.  The  entire  money  value  of 
the  production  of  gold  is  insignificant  when  compared  to  the 
market  value  of  the  golden  butter  produced  throughout  the 
world  in  the  same  time — and  yet  butter  is  only  one  of  the 
products  of  milk,  though  the  one  that  most  extensively  enters 
commerce. 

3.  MILK  is  chemically  a very  complex  liquid,  and  in  its 
nature  PERISHABLE.  After  evaporation  in  vacuum  pans,  with 
the  addition  of  sugar,  it  can  be  shipped  far  and  kept  for  a long 
time.  By  freezing  it  has  also  been  shipped,  especially  from 
Denmark  to  England.  But  the  most  rational  course  consists 
in  the  shipment  of  the  two  most  valuable  and  permanent  pro- 
ducts, butter  and  cheese,  and  to  use  the  balance  for  food  on 
the  farm. 

4.  THE  PROXIMATE  ANALYSIS  of  milk  has  been  practiced 
from  time  immemorial;  upon  it  rests  the  milk  industry.  By 
simply  allowing  milk  to  stand  in  a cool  place,  its  lightest  parts, 
CREAM,  rise  to  the  surface,  forming  a layer  of  about  one-tenth 
the  depth  of  the  milk.  This  cream,  after  ripening,  yields 
BUTTER  by  simply  churning.  The  skim-milk,  on  spontaneous 
or  artificial  acidification,  yields  CASEIN  (cheese) ; the  whey 
left  gives,  upon  concentration,  milk  sugar  (LACTOSE)  in 
crystals,  and  SALTS  (potassium  phosphate,  chloride)  as 
residue. 

5.  By  the  introduction  of  modern  CENTRIFUGAL  SEPAR- 
ATORS, the  stream  of  fresh  milk  flowing  into  the  machine 
comes  out  in  two  continuous  streams,  namely,  the  lighter  cream 
from  the  inner,  the  heavier  skim -milk  from  the  outer  sheet. 
The  Laval  separator  makes  fully  one  hundred  revolutions  a 
second,  thus  instantly  separating  milk  into  its  two  layers  for 
which  the  less  intense  gravity  requires  twenty-four  hours. 


MILK  AND  BUTTER. 


281 


G.  The  microscope  shows  that  milk  is  an  (opaque,  white) 
EMULSION;  a transparent,  aqueous  solution  holding  minute 
fat  (butter)  globules  in  suspension.  These  globules  are 
each  covered  with  a thin  film,  which  readily  yields  to  alkalies, 
after  which  the  ether  will  dissolve  the  fat  and  leave  it  upon 
spontaneous  evaporation.  While  not  the  most  exact,  this  is 
the  most  instructive  determination  of  the  per  cent,  of  butter 
in  milk. 

7.  By  such  processes  it  has  been  ascertained  that  GOOD 
COW  MILK  contains  about  13  per  cent,  of  the  four  solids  con- 
stituents specified;  the  balance  (87  per  cent.)  being  water. 
The  percentage  of  the  four  solids  averages  as  follows:  fat,  4 
(butter);  sugar,  5 (lactose);  curd,  3j  (casein),  and  salts,  h 
Human  milk  contains  about  one  per  cent,  more  of  sugar  (6) 
and  one  per  cent,  less  of  casein  (2j);  it  is  more  sweet  and 
much  more  easily  assimilated  than  cow’s  milk. 

8.  FRESH  MILK  is  sweet  and  faintly  alkaline;  G 1.03. 
By  exposure  it  becomes  acid;  LACTIC  ACID  forming  (best 
between  25  and  35  degrees).  In  proportion  as  this  acid  forms, 
the  casein  is  precipitated  (coagulated).  After  straining  and 
washing,  this  CRUDE  CASEIN  may  be  purified  by  dissolving 
it  in  a strong  solution  of  sodium  carbonate  at  a moderate  tem- 
perature. After  removing  fats,  and  other  impurities,  the 
casein  may  be  obtained  by  precipitation  with  an  acid,  and 
washed  with  water,  alcohol  and  ether. 

9.  CHEESE  consists  mainly  of  the  casein  of  milk.  If  made 
from  skim-milk,  the  cheese  is  hard,  almost  like  a brick;  it  is 
said,  “dogs  bark  at  it,  hogs  grunt  at  it,  but  neither  dare  bite 
it.”  Made  from  whole  milk,  it  retains  all  the  fat,  and  is  both 
palatable  and  nourishing.  By  various  additions  and  peculiar 
processes  of  ageing,  numerous  varieties  of  cheese  are  pro- 
duced. Some  districts  are  famous  for  their  special  brands  of 
cheese  that  bring  deservedly  a high  price  in  the  market. 

10.  BUTTER  is  the  most  complex  and  the  most  easily 
assimilated  fat  known;  hence  the  high  price  it  brings,  and 


282 


LECTURE  68. 


hence  also  the  multiform  attempts  to  imitate  it.  Genuine 
butter  has  a specific  aroma  and  rich  golden  color;  G 0.94,  F 
31,  solidifying  at  20.  It  contains  56  per  cent,  solid  fats 
(stearin  and  palmitin),  36  per  cent,  of  olein,  and  8 per  cent, 
of  butyrin  with  certain  other  light  fats  and  flavoring  ingredients 
well  known  to  the  connoisseur,  but  not  scientifically  defined. 

11.  The  real  VALUE  OF  BUTTER  depends  upon  the  judg- 
ment and  taste  of  the  consumer;  if  the  consumer  does  not 
know  good  butter  from  indifferent  or  bad,  or  genuine  from 
spurious,  he  will  be  satisfied  with  the  low  grades  and  imita- 
tions. The  chemist  can  only  detect  rather  glaring  frauds. 
When  we  come  to  the  study  of  the  fatty  acids,  we  shall  learn 
to  understand  this. 

12.  Since  1870,  the  market  is  flooded  with  ARTIFICIAL 
BUTTERS,  including  ox-butters,  hog-butters  and  worse.  The 
term  butter  having  an  established  signification,  its  use  for  any 
chemical  imitations  is  in  its  very  nature  fraudulent;  legislation, 
even  in  Germany,  is  now  beginning  to  recognize  this  fact. 
But  specially  feeding  cows  low  grade  fats  (cotton  seed  oil 
cakes,  etc.,  etc.)  adds  to  fraud  the  contemptible  attempt  to 
make  the  innocent  cow  a particeps  criminis. 


68.  FLESH  AND  BLOOD. 

1.  The  highest  material  life  on  the  globe  is  represented  by 
the  warm  blooded  animals.  Man  has  taken  their  flesh  as  food; 
first  as  a hunter,  next  as  herdsman,  and  now  as  farmer. 
The  domestic  animal  occupies  a conspicuous  and  most  im- 
portant place,  both  in  the  permanence  of  soil  fertility  and  in 
the  immediate  financial  rewards.  THE  WEALTH  OF  modern 
NATIONS,  as  was  that  of  the  patriarchs,  is  largely  represented 
in  the  number  of  their  cattle. 

2.  The  primitive  process  of  drying,  salting  and  smoking, 
permit  the  PRESERVATION  OF  perishable  MEATS  beyond  the 


FLESH  AND  BLOOD. 


283 


day  of  procurement  and  thus  also  their  entrance  in  the  com- 
merce of  the  world.  The  modern  process  by  refrigeration 
permits  transcontinental  and  oceanic  shipment  of  so-called 
“fresh  meats;”  but  the  product  suffers  really  more  than  by 
the  older  methods.  It  has  built  up  great  trusts,  depressed  both 
local  industry  and  agriculture,  and  is  fast  depriving  the  rising 
generation  of  the  knowledge  of  genuine  beef. 

3.  The  old  sage  said  BLOOD  IS  THE  LIFE  OF  THE  FLESH 
(Gen.  9,  4)  ; modern  investigations  have  fully  substantiated 
this  statement.  Blood  is  the  most  wonderful  liquid  of  nature. 
Our  scientific  methods  are  crude  when  applied  to  this  liquid; 
in  modern  days  we  have,  through  the  investigations  of 
PASTEUR  (p.  31)  and  his  disciples,  obtained  many  demon- 
strations of  the  Mosaic  statement. 

4.  BLOOD  is  a most  complex  liquid,  G 1.05  — 1.07;  its 
odor  is  specific,  varying  with  the  animal.  In  every  (warm 
blooded)  animal  blood  presents  two  strikingly  different  modi- 
fications: bright  red  in  the  arterial  system,  flowing  from  the 
heart  to  the  substance  of  the  flesh,  and  darker,  blueish  in  the 
return  current  of  the  venous  system.  Each  of  these  modifi- 
cations shows  its  own  specific  absorption  spectrum  between 
D and  E (52,  12). 

5.  A small  drop  of  blood,  spread  out  by  the  cover  glass, 
shows  under  a good  microscope,  a multitude  of  minute  disk- 
like GLOBULES  or  CORPUSCLES.  In  human  blood  there  are 
about  five  millions  of  globules  to  the  droplet  (of  one  cubic  milli- 
meter), each  globule  being  8 microns  in  diameter  and  2 
microns  thick.  In  most  mammals  the  globules  are  also  circu- 
lar disks.  In  birds,  reptiles  and  fishes  their  form  is  elliptical, 
and  often  much  larger  than  in  man.  In  frogs  their  larger 
diameter  is  22  microns. 

6.  Freshly  drawn  blood,  left  standing  in  a glass  cup,  gradu- 
ally separates  into  the  semi-solid,  red  CLOT  and  the  pale- 
yellow  liquid  SERUM.  The  clot  (on  washing)  leaves  white 
FIBRIN;  in  the  water  the  globules  settle  like  starch.  The 


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LECTURE  68. 


serum  will  also  coagulate  when  exposed  long  enough.  Human 
blood  contains  12.7  per  cent,  of  globules,  and  0.3  per  cent, 
fibrin  in  the  clot,  and  7 per  cent,  albumin  in  the  serum ; total 
20  per  cent,  solids,  and  80  per  cent,  water. 

7.  Serum,  when  gently  heated,  coagulates ; the  whitish  solid 
is  mainly  ALBUMEN.  The  white  of  eggs  shows  the  same  de- 
portment to  heat.  The  albumens  are  distinguished  as  egg- 
and  serum-albumen.  They  differ  slightly,  especially  in  their 
resistance  to  a rise  in  temperature.  Egg  albumen  coagulates 
more  readily  (at  a lower  temperature)  than  serum -albumen. 
Methods  of  purification  cannot  here  be  given. 

8.  The  blood  globules  are  covered  with  a thin  fibrinous 
membrane,  and  consist  of  red  HEMOGLOBIN  and  the 
albumen -like  substance  globulin  in  the  proportion  of  about 
8 to  1.  Haemoglobin  is  the  real  coloring  matter  of  the  blood. 
Shaking  fresh  blood  in  a flask  with  a small  amount  of  ether,  the 
globules  are  broken  up ; when  the  flask  is  set  aside  for  a night 
in  the  cold  (best  in  melting  ice)  crystals  of  haemoglobin  will 
be  found  on  the  walls  of  the  flask.  The  crystals  contain  iron. 

9.  A dilute  acqueous  solution  of  haemoglobin  ABSORBS 
OXYGEN  gas,  and  becomes  brilliant  red,  showing  two  dark 
absorption  bands  one  each  near  D and  F.  Any  REDUCING 
GAS  drives  out  the  oxygen,  the  color  changes  to  that  of  dark 
blood,  and  a broad  absorption  band  appears  midway  between 
D and  E,  instead  of  the  two  bands  characterizing  the  red  or 
oxyhemoglobin.  These  changes  can  be  exhibited  repeatedly 
in  succession. 

10.  The  blood  also  contains  MINERAL  MATTER,  left  upon 
incineration.  The  clot  gives  mainly  iron  and  potassium  com- 
pounds; both  leave  phosphates  and  chlorides.  The  serum 
gives  sodium  salts. 

Salt  solutions  exert  a remarkable  effect  on  blood.  Blood 
run  into  ten  times  its  own  volume  of  a 2 per  cent,  salt  solution 
does  not  coagulate;  the  globules  settle  to  the  bottom  of  this 
mixture. 


FLESH  AND  BLOOD. 


285 


11.  The  muscular  tissue  is  built  up  from  blood;  the  mus- 
cular fiber  is  related  to  fibrin.  Again,  the  used  up  parts  are 
removed  by  and  in  the  blood,  partly  serving  a further  purpose 
in  the  hepatic  system  (BILE)  in  aid  of  digestion,  partly  being 
removed  through  the  kidneys  (URINE),  skin  (PERSPIRATION) 
and  lungs  (RESPIRATION).  We  shall  very  briefly  consider 
the  chemical  processes  involved  in  a subsequent  lecture. 

12.  Albumen,  fibrin  and  casein,  as  well  as  their  modifica- 
tions, are  called  albuminoid  substances,  also  PROTEIDS, 
nitrogenous  substances,  plastic  food,  etc.,  etc.  Singeing 
them,  they  emit  the  characteristic  odor  (I,  5).  They  are 
extremely  prone  to  change.  We  distinguish  them  mainly 
by  their  most  common  mode  of  solidification  or  coagulation ; 
albumen  by  heat,  casein  by  acids,  and  fibrin  by  mere  exposure 
to  the  air. 


69.  BONE  AND  SINEW. 

1.  The  deep  contains  animals  depending  on  the  sur- 
rounding medium  for  support  and  even  form;  their  body 
consisting  of  flesh  and  blood  only.  But  all  higher  animals, 
from  the  fish  of  the  sea  to  the  bird  of  the  air,  have  their  flesh 
connected  by  strong  SINEWS  to  a frame  work  of  BONES, 
whereby  they  show  infinitely  varied  beauty  of  form  and  per- 
fection of  mechanism. 

2.  The  dominant  form  of  bone  is  the  TUBE.  Galilei  has 
shown  this  form  to  be  the  most  economical,  giving  the  greatest 
possible  strength  for  the  amount  of  material  employed.  The 
material  itself  is  also  most  perfect,  being  a living  tissue  of 
mineral  (S)  and  organic  (i)  matter,  possessing  both  STRENGTH 
AND  ELASTICITY  in  a high  degree. 

3.  The  mineral  matter  of  a bone  is  dissolved  in  dilute  (10 
per  cent.)  muriatic  acid  in  the  course  of  a few  days.  The 
liquid  shows  mainly  calcium  phosphate  (85  per  cent.)  and 


286 


LECTURE  69. 


carbonate  (11  per  cent.);  the  balance  being  about  equally 
calcium  fluoride  and  magnesium  phosphate.  The  well  washed 
organic  material,  OSSEIN,  retains  the  form  of  the  bone  used, 
but  is  flexible  and  elastic,  so  that  it  may  even  be  tied  in  a 
knot.  • 

4.  Boiling  ossein  in  water,  converts  it  into  GELATIN, 
which  is  soluble  in  hot  water,  but  solidifies  to  a jelly  upon 
cooling.  When  the  gelatin  solution  is  so  dilute  that  it  does 
not  set  to  a jelly  on  cooling,  an  aqueous  solution  of  tannin 
will  give  a most  characteristic,  white  flocculent  precipitate. 
Alcohol  also  precipitates  dilute  solutions  of  gelatin. 

5.  The  white  fibers  of  connective  tissue  (sinews  and  ten- 
dons) are  mainly  composed  of  COLLAGEN,  that  is,  a substance 
which  changes  the  gelatin  when  boiled  with  water.  When 
connective  tissue  is  treated  with  acetic  acid,  the  white  fibers 
swell  up  and  become  transparent,  while  the  elastic  fibers 
(elastin)  remain  unchanged  and  can  be  seen  distinctly  under 
the  microscope. 

6.  Gelatins  of  greatly  varying  qualities  are  manufactured, 
bringing  correspondingly  different  prices.  From  the  low  grades 
of  GLUE,  the  prices  run  up  to  divers  fine  brands  of  GELATIN 
for  culinary  purposes  and  for  clarifying  liquids.  The  purest 
and  most  costly  is  the  genuine  Russian  Beluga  ISINGLASS, 
made  from  the  swimming  bladder  of  certain  sturgeons. 

7.  When  these  gelatins  had  first  been  extracted,  especially 
from  bones  under  pressure,  they  were  recommended  by 
chemists  as  cheap  and  good  foods  for  the  poor.  These  foods 
were  introduced  into  penal  and  charitable  institutions,  to  the 
great  disgust  of  the  inmates,  whose  unsophisticated  stomachs 
were  denounced  as  prejudiced,  till  the  rats  in  a raid  ate  all  in 
sight  but  this  “bone  soup.”  GELATIN  IS  NO  FOOD. 

8.  The  substance  of  horn  and  hoof,  feathers  and  hair,  and 
of  the  epithelial  tissues  generally,  are  less  soluble  and  contain 
sulphur;  when  boiled  with  water  under  pressure  they  yield 


BONE  AND  SINEW. 


287 


sulphuretted  hydrogen.  These  substances  are  called  KERA- 
TINS. From  feathers,  a brownish-yellow  keratin  is  prepared 
for  coating  pills.  Such  pills  are  not  acted  upon  in  the  stomach, 
and  permit  the  introduction  of  remedial  substances  to  the 
intestines. 

9.  Silk,  the  most  costly  fiber,  is  manufactured  by  the  silk 
worm  from  mulberry  leaves.  It  consists  of  a smooth,  round, 
thread  (fibroin)  covered  with  sericin  or  silk-glue.  The  latter 
is  readily  dissolved  by  soap  solutions  to  a sort  of  glue,  while 
the  former  resists;  both  are  rapidly  dissolved  by  alkalies,  but 
are  much  less  acted  upon  by  acids.  Silk  is  very  hygroscopic. 
An  “artificial  silk”  is  made  from  collodion. 

10.  Bones  burnt  in  an  open  fire  leave  about  two-thirds  of 
white  BONE-ASH.  This  is  used  for  cupels  (7.6)  and  for  the 
extraction  of  phosphorus.  This  method  of  extraction  was  first 
devised  byScheele.  By  sulphuric  acid  much  lime  (as  gypsum) 
is  removed  from  the  bone  ash;  the  phosphate  solution  is  evap- 
orated to  a syrup,  and  in  two  stages  reduced  by  charcoal. 

11.  Bones  heated  with  exclusion  of  the  air  leave  BONE 
BLACK  or  animal  charcoal,  and  yield  an  offensively  smelling 
distillate,  Dippel’s  oil.  The  charcoal  results  from  the  organic 
material,  the  ossein,  and  retains  all  the  mineral  matter. 
Animal  charcoal  is  a most  important  absorbent  for  coloring  and 
odoriferous  substances,  and  hence  constantly  used  as  filter  for 
organic  liquids  in  the  laboratory  and  in  the  arts  (sugar 
refmeges) . 

12.  Animal  charcoal,  having  been  used,  may  be  REVIVED 
by  first  washing  it  out  and  then  charring  it  again.  This  pro- 
cess is  even  repeated,  on  account  of  the  high  price  of  the 
material.  When  finally  no  longer  fit,  even  as  admixture  to 
fresh  animal  charcoal,  it  may  be  used  as  a source  of  phos- 
phorus. ' Bones  are  also  utilized  by  first  extracting  the  fat 
with  benzol,  then  the  ossein  with  water,  and  lastly,  the 
phosphorus  as  indicated  above. 


70.  ANIMAL  AND  PLANT. 


1.  We  have  seen  in  what  manner  the  principal  prime  ma- 
terials of  organic  chemistry  are  extracted  from  plants  and 
animals,  and  how  they  are  purified.  They  yield  chemical 
compounds  of  perfectly  definite  chemical  and  physical  prop- 
erties. 

2.  Before  we  begin  a more  detailed  study  of  the  chemical 
transformation  of  these  prime  materials,  it  will  be  advisable  to 
look  upon  their  mutual  relations  in  the  GREAT  CIRCLE  OF 
MATERIAL  LIFE.  Air,  water  and  soil  we  shall  find  to  be  the 
substances,  sunshine  the  power,  and  the  living  cell  the  labora- 
tory in  which  this  chemical  circulation  of  matter  takes  place. 

3.  PLANTS  GROW  from  seeds.  These  seeds  are  very 
small  compared  to  the  plant.  The  substance  of  the  oak  was 
never  contained  in  the  acorn.  Burning  the  wood  of  the  tree, 
we  obtain  heat  (FIRE)  as  power,  also  carbon  dioxide  and  water 
as  material  products  disappear  in  the  atmosphere;  finally  a 
few  per  cent,  of  mineral  matter  (ASHES)  remain  as  visible 
solids  of  the  wood  burned. 

4.  This  rapid  destruction  (combustion)  of  the  plant  we 
now  know  to  be  the  exact  opposite  of  its  slow  growth.  The 
SUN  supplies  the  heat  necessary  to  unite  aqueous  vapor  and 
carbon  dioxide  of  the  AIR  to  the  combustible  material  of  the 
plant  under  separation  of  oxygen  gas;  the  soil  supplies  the 
MINERAL  MATTER  remaining  in  the  ashes. 

5.  Numerous  LABORATORY  EXPERIMENTS  on  growing 
plants  in  glass  cylinders,  permitting  an  accurate  determination 
of  the  changes  effected  on  the  air  supplied,  have  proved  this. 
The  effects  of  mineral  matter  have  been  specially  studied  by 
growing  plants  (beans,  Indian  corn,  etc.)  in  dilute  solutions  of 
accurately  known  mineral  composition  (Sachs),  confirming  the 
earlier  chemical  results  (Liebig,  p.  23)  on  ashes  and  soils. 


ANIMAL  AND  PLANT. 


■289 


6.  That  growing  PLANTS  EXHALE  OXYGEN  GAS  can 
readily  be  seen  by  examining  the  gas  accumulating  over  any 
green  foliage  under  water  and  exposed  to  the  sun  light.  A 
simple  funnel  suffices  to  hold  the  foliage.  The  gas  accumu- 
lating in  the  stoppered  neck  of  the  funnel  re-kindles  a glow- 
ing shaving  when  the  stopper  is  withdrawn.  It  is  oxygen. 

7.  The  comparatively  small  amount  of  nitrogenous  material 
produced  in  the  plant  (especially  stored  in  its  seeds)  has  been 
traced,  in  like  manner,  to  the  AMMONIA  of  the  air  and  in  the 
soil.  Hence  the  beneficent  effects  of  animal  manures.  The 
fertility  of  the  soils  of  Europe  is  sufficiently  enhanced  by 
guano  to  warrant  the  importation  thereof  from  the  opposite 
extremity  of  the  globe. 

8.  The  herbivorous  and  grain  eating  animals  depend  for 
their  food  entirely  on  the  plants;  even  carnivorous  animals  do 
so,  because  their  prey  subsist  on  plant  food.  But  animals 
require  equally  a pure  air,  rich  in  ox^/gen,  for  respiration. 
Without  VEGETABLE  FOOD,  animals  slowly  starve  to  death; 
without  OXYGEN,  they  die  promptly  from  suffocation. 

9.  Throughout  the  system  of  the  animal,  the  absorbed 
vegetable  food  (chyle)  and  the  oxygen  of  the  air  unite  chem- 
ically; the  red  blood  becomes  dark  from  the  products  of  this 
combination.-  In  the  LUNGS  the  carbon  dioxide  is  sent  back 
to  the  atmosphere  (16.  9).  In  the  KIDNEYS  the  products  of 
the  combination  of  nitrogenous  substances  or  proteids  are 
separated  (urea,  uric  acid).  The  SKIN  largely  removes  the 
water  in  prespiration.  Undissolved  food  RESIDUES  are  evacu- 
ated as  feces.— See  blackboard  diagram. 

10.  The  union  of  the  vegetable  food  with  the  oxygen  of 
the  air  throughout  the  system  constitutes  a real  wet-way 
combustion,  and  produces  the  HEAT  AND  MUSCULAR  POWER 
-of  the  body.  The  first  experimental  researches  in  this  field 
were  made  by  Lavoisier  (p.  19).  Grimaux  has  published  two 
most  instructive  plates  in  his  Life  of  Lavoisier,  showing  these 
remarkable  experiments. 


290 


LECTURE  71. 


11.  It  is  evident  that  animal  life  contains  within  itself  the 
CAUSES  OF  ITS  OWN  DESTRUCTION  or  death.  The  air 
exhaled  poisons  the  atmosphere.  In  a like  manner,  the  other 
products  of  animal  life  are  poisonous  to  such  life.  While 
plants  are  less  sensitive,  vegetable  life  alone  would  also  pro- 
duce conditions  destructive  to  itself. 

12.  Thus,  not  only  does  animal  life  depend  upon  plants  for 
food,  but  even  for  constantly  destroying  the  poisonous  effects 
of  animal  life  on  itself  and  its  surroundings.  In  a like  manner 
animal  life  makes  it  possible  for  vegetation  to  flourish.  The 
two  forms  of  life  supplement  each  other  to  one  grand  circle  of 
chemical  and  physical  transformations,  depending  for  its 
permanence  on  that  of  the  sun. 


71.  FERMENTATION  AND  LIFE. 

1.  Bread  and  wine  have  nourished  and  refreshed  man  from 
the  earliest  times.  Both  substances  involve  chemical  processes 
of  great  mystery.  The  grain  and  the  grape  furnished  by 
plant-life,  have  undergone  an  additional  chemico-vital  process 
before  they  became  fit  for  food.  This  process  is  FERMEN- 
TATION. 

2.  Moses  prohibited  the  use  of  leavened  bread  during  the 
exodus.  It  was  also  prohibited  in  burnt  meat  offerings. 
These  are  probably  the  oldest  historic  records  of  LEAVEN. 
The  wonderful  rapidity  wherewith  “a  little  leaven”  changes 
a large  amount  of  meal,  is  used  repeatedly  as  a striking 
figure  in  the  new  testament.  The  fermentation  of  grape  juice 
was  practiced  as  far  back  as  the  flood. 

3.  Van  Helmont  (p.  30)  is  the  first  modern  investigator 
who  reached  a fair  conception  of  the  importance  of  fermentation 
in  the  economy  of  nature;  he  rightly  compared  VITAL 
PROCESSES  in  health  and  disease  to  fermentation.  The 
microscope  afterwards  showed  the  presence  of  special  cells  in 


FERMENTATION  AND  LIFE. 


291 


leaven  and  ferment.  But  even  Liebig  (1870)  considered  these 
cells  non-essential  to  the  chemical  process  going  on. 

4.  It  is  Pasteur  (p.  31)  who  has  discovered  the  true 
function  of  ferments  in  nature’s  household.  In  fermentation 
we  have  the  life  process  of  the  cell.  The  ferment  cell  feeds 
on  glucose;  the  products  of  its  vital  act  are  carbon  dioxide  and 
alcohol.  To  grow,  the  ferment  cell  requires  nitrogenous  food 
and  salts,  as  do  higher  plants.  Pure  glucose  solution  will  not 
ferment. 

5.  TFIE  GERMS  of  ferments  float  in  the  air.  Solutions, 
sterilized  by  boiling  in  glasses  loosely  stoppered  with  cotton, 
will  not  ferment;  the  germs  possibly  present  being  killed  by 
the  heat,  and  germs  from  the  air  being  stopped  by  the  cotton. 
Even  a downward  bent  neck  prevents  the  germs  from  falling 
into  the  flask.  There  is  no  spontaneous  generation.  Thus 
Pasteur  in  the  sixties. — Tyndall  strikingly  showed  the  germ 
filtering  effect  of  cotton  on  air.  The  nose  is  such  a germ  filter 
for  our  own  lungs. 

6.  The  most  common  ferments  for  wine,  beer  and  bread 
are  globular  or  elliptical,  acting  on  the  saccharine  substanses; 
hence  they  are  called  SACCHAROMYCES.  The  beer  yeast 
contains  the  S.  cerevisiae,  consisting  of  almost  spherical  cells, 
growing  by  budding  while  young,  forming  nuclei  when  old 
(see  plate).  The  wine  ferment,  S.  ellipsoideus,  is  named 
after  the  elongated  form  of  its  cells. 

7.  At  common  temperatures  (16  to  20  degs.)  beer  wort 
ferments  rapidly,  the  yeast  rising  to  the  SURFACE.  At  lower 
temperatures  (6  to  8 degs.),  the  wort  ferments  slowly,  requir- 
ing weeks  instead  of  days;  the  yeast  collects  at  the  BOTTOM. 
The  beer  produced  in  the  latter  case  is  called  lager.  The 
ferment  of  surface  fermentation  differs  from  that  of  bottom 
fermentation.  Both  are  present— but  each  grows  best  at  its 
own  temperature. 

8.  Beer  or  light  wine  exposed  to  air  becomes  sour;  acetic 
acid  is  formed,  due  to  the  growth  of  BACILLUS  ACETICUS, 


292 


LECTURE  71. 


which  thrives  best  (optimum)  between  18  and  35  degrees, 
and  requires  air  (aerobic  ferment).  The  souring  of  milk  is 
due  to  the  formation  of  lactic  acid  from  its  lactose;  this  change 
is  due  to  the  growth  of  BACILLUS  ACIDI  LACTICI,  which 
requires  no  air  (anaerobic  ferment)  and  thrives  best  between 
35  and  40  degrees.  (See  plate). 

9.  The  life  process  of  ferments  limits  itself  by  AUTOTOXY, 
precisely  as  does  the  life  process  of  true  plants  and  animals. 
When  10  to  12  per  cent,  (by  weight)  of  alcohol  has  been 
produced  in  the  glucose  solution,  the  cells  cease  growing; 
when  14  per  cent,  are  present,  the  ferment  is  killed  by  its 
own  product.  The  most  favorable  tem.perature  for  the  growth 
of  the  ferment  cells  is  between  28  and  34  degrees  (the  opti- 
mum). In  concentrated  glucose  solutions  (over  60  per  cent.) 
the  cells  cannot  live. 

10.  Pasteur  has  also  proved  that  certain  contagious  and 
infectious  DISEASES  are  fermentative;  and  that  the  system 
may  be  protected  against  the  growth  of  these  ferments  or 
microbes  by  VACCINATION.  The  immunity  enjoyed  by  our 
race  against  smallpox,  since  Jenner’s  day,  can  now  be  under- 
stood. The  microbe  is  attenuated  (weakened)  by  culture 
under  unfavorable  conditions;  the  liquid  (serum)  so  produced 
may  confer  immunity  to  the  system  to  which  it  is  transferred 
(by  inoculation,  vaccination). 

11.  Medical  research  of  the  present  is  almost  entirely 
dominated  by  the  METHODS  OF  THE  CHEMIST  PASTEUR. 
Microbes,  toxins,  antitoxins,  serums  are  the  watchwords  of 
the  day  and  the  chemist  properly  surrenders  this  new  world 
to  the  physician  and  the  biologist.  But  the  new  compounds 
produced — corresponding  to  alcohol  in  common  fermentation — 
remain  in  the  chemical  laboratory. 

12.  Thus,  many  of  these  microbes  produce  alkaloidal 
compounds.  If  formed  during  life  of  the  macro-organism, 
these  compounds  are  called  LEUCOMAINS  (Gautier) ; if  in  the 
cadaver,  they  are  called  PTOMAINES,  (Selmi).  Several  of 


FERMENTATION  AND  LIFE. 


293 


these  latter  simulate  the  solubilities  and  color  reactions  of  the 
true  vegetable  alkaloids,  strychnine,  quinine,  and  others,  and 
thus  impose  extra  care  on  the  part  of  the  toxicologists.  The 
former  also  show  a like  kinship;  the  leucomains  xanthin  and 
uric  acid  give  the  same  murexid  test  as  do  theobromine  and 
caffeine  (theine).  This  may  account  for  the  general  use  of 
tea,  coffee  and  chocolate. 


72.  PETROLEUM  AND  COAL. 

1.  Plants  and  animals  have  lived  on  this  globe  for  ages; 
we  find  their  imperishable  remains  in  all  stratified  rocks  (12). 
Such  remains  are  called  FOSSILS  and  casts,  according  as  it  is 
the  original  material  (shell,  coral,  bone),  or  the  same  replaced 
by  some  other  substance  (silica). 

2.  Many  limestone  deposits  are  almost  completely  made  up 
of  shells  and  corals,  due  to  the  respiration  of  mollusks  and 
polyps  of  the  primeval  sea.  These  enormous  limestone  de- 
posits thus  contain  the  carbon  dioxide  of  the  PRIMEVAL 
ATMOSPHERE,  which  must  have  been  utterly  irrespirable  to 
warm  blooded  animals. 

3.  In  such  an  atmosphere,  vegetation  must  have  been  ex- 
cessively luxuriant.  The  numerous  coal  deposits  found  in  all 
parts  of  the  globe  confirm  this  conclusion  by  their  extent  and 
thickness;  for  COAL  is  the  fixed  residue  of  primeval  vegeta- 
tion, terrestrial  and  aquatic.  Enclosed  between  two  layers  of 
rock,  the  vegetable  material  would  mainly  lose  volatile  con- 
stituents and  become  richer  in  carbon  (carbonized). 

4.  Chemically  we  can  distinguish  only  two  kinds  of  coal, 
namely,  BROWN -COAL  and  bituminous  or  BLACK-COAL, 
The  first  gives  an  acid  distillate  (acetic  acid) ; when  heated  in 
a test  tube,  a moist  blue  litmus  paper  is  reddened  by  the 
vapors.  The  second  gives  a strongly  alkaline  (ammoniacal) 
distillate.  Anthracite  seems  to  be  the  end-product  of  bitu- 
minous coal. 


294 


LECTURE  72. 


5.  Mohr,  the  systematize!'  of  volumetric  Analysis  (50,  1), 
found  that  wood  and  peat  yield  acid  distillates,  while  dried 
sea  weeds  yield  an  alkaline  distillate.  He  concluded  that  it 
is  chemically  impossible  to  derive  bituminous  coal  from  wood  or 
peat;  that  this  coal  must  have  formed  in  the  ocean  from  SEA 
WEEDS  and  still  continues  so  to  form  to-diy  (Sargossa  Sea  of 
the  Atlantic) . 

My  own  observations  and  analyses  (48,  10)  have  confirmed 
the  conclusions  of  Mohr.  However,  geologists  continue  to  dis- 
regard the  apparent  chemical  impossibility  involved  in  their 
favorite  theory  of  the  origin  of  coal  from  trees  of  primeval 
forests  and  from  peat  bogs. 

6.  Chemically  coal  is  a prime  material  of  the  utmost  im- 
portance (12,  10).  It  forms  the  basis  of  most  extended 
chemical  industries.  GAS  WORKS  yield  tar,  ammonia, 
cyanides  and  other  products.  The  use  of  coal  as  fuel  — and 
source  of  steam  power — ^may  be  again  replaced  by  water 
power,  which,  converted  into  electricity,  may  be  widely  dis- 
tributed, as  is  being  done  at  the  present  (Niagara). 

7.  AT  Baku,  on  the  Caspian  Sea,  fire  worshipers  have 
maintained  permanent  fires  from  time  immemorial.  Over 
quite  an  extended  region  it  is  sufficient  to  dig  or  drill  down  a 
few  feet  into  the  ground  to  obtain  a flow  of  gas  that  burns 
upon  being  lit.  The  Chinese  have  for  centuries  utilized  such 
ho-tsings  (tire-springs)  in  connection  with  their  salt  works. 

8.  Shortly  before  1860,  PETROLEUM  was  discovered  in 
enormous  quantities  in  Pennsylvania,  and  promptly  refined 
for  the  market  of  the  world  as  illuminating  oil  (KEROSENE). 
New  wells  were  drilled,  great  fortunes  were  made,  and  oil 
fields  sought  for  in  other  States.  New  York,  Ohio,  Canada 
and  California  have  added  to  the  production. 

9.  The  example  of  America  found  imitators  in  the  Baku 
region,  which  now  is  commercially  highly  developed.  The 
oil  is  transported  by  a pipeline  to  the  Black  Sea,  and  shipped 
by  tank-vessels.  This  last  method  has  been  adopted  by  the 


PETROLEUM  AND  COAL. 


295 


American  firms  for  export  to  Europe.  The  Rothschilds  (with 
Nobel  as  engineer)  control  the  RUSSIAN  OIL;  the  Standard 
Oil  Company  (Rockefeller)  controls  the  AMERICAN  OIL. 
The  two  have  divided  the  market  of  the  world  between  them. 

10.  The  total  PRODUCT  OF  PETROLEUM  is  about  fifty 
million  barrels  a year,  of  which  America  produces  about  30, 
Russia  about  20  million  barrels.  Galicia  and  Roumania  pro- 
duce half  a million,  Canada  a quarter  million  barrels.  Nobel 
has  given  millions  of  dollars  to  the  University  of  Stockholm; 
Rockefeller  has  done  the  same  for  the  University  of  Chicago. 
Thus  petroleum  will  continue  to  give  light. 

11.  THE  CRUDE  PETROLEUM  is  a limpid  to  thick  liquid, 
not  miscible  with  water.  G 0.79  to  0.94.  Wine  colored  to 
black.  Etherial  to  offensive  odor. 

American  petroleum  is  lighter  colored  and  lighter  weight, 
and  gives  about  twice  as  much  kerosene  as  the  Russian;  the 
latter  leaves  almost  ten  times  as  much  of  residue,  non-vola- 
tile at  300°. 

12.  PETROLEUM  IS  REFINED  by  fractional  distillation. 
The  fraction  passing  over  between  150  and  300°  is  kerosene, 
fit  for  illuminating  purposes.  It  is  further  purified  by  washing 
with  sulphuric  acid,  then  with  water,  finally  with  dilute  caus- 
tic soda;  lastly  re-distilled.  American  kerosene  is  nearly 
colorless,  blueish  fluorescent;  G 0.79  — 0.80,  flash-point 
above  21  degrees. 


73.  GAS  AND  TAR. 

1.  THE  ILLUMINATION  of  the  streets  of  cities  is  peculiar 
to  modern  times.  The  streets  of  Paris  were  the  first  illum- 
inated (in  1667).  Stationary  oil  lamps  or  lanterns  were  used, 
after  attempts  to  make  each  householder  keep  a light  burning 
all  night  in  one  window  had  failed. 


296 


LECTURE  73. 


2.  When  the  handling  of  gases  had  become  familiar 
towards  the  close  of  last  century,  it  was  natural  to  try  to  dis- 
tribute by  tubes  the  gas  driven  off  by  heat  from  combustibles 
for  illuminating  and  heating  purposes.  Philip  LEBON  in 
France,  Murdoch  and  Samuel  CLEGG  in  England  perfected 
plans  and  appliances.  The  inventions  of  the  latter  continue 
in  use  even  to-day. 

3.  THE  STREETS  OF  LONDON  were  illuminated  by  gas  in 
1812;  those  of  Paris  in  1815.  Now  even  most  small  towns 
are  illuminated  by  gas.  IN  ENGLAND,  ten  million  tons  of  coal 
are  used  annually  for  making  about  three  thousand  million 
cubic  meters  of  gas;  four  hundred  million  dollars  capital  • 
being  invested  in  the  six  hundred  gas  works  of  England. 


Uloc  de  bouille  reprdsentd  avec  le  volume  proportionnel  Jes  priocipaux  produits  qu’pn  en  retire. 

1.  Bloc  de  hduille.  — 2.  Goudron.  — 3.  Huile  Idgdre — 4.  Huile  lourde.  — o.Graisse  verte  ou  huile  4 anthracene.  —6.  BeBzine. 
— 7.  Toluene.  — 8.  Phenol.  — 9.  Naphtaline.  — 10.  Anthracene.  (O'apres  les  dchantillons  de  la  conference  de  U.  Wurti.) 


GAS  AND  TAR. 


297 


4.  THE  ILLUMINATING  GAS  produced  represents  only 
about  18  per  cent,  of  the  weight  of  the  bituminous  coal  taken. 
About  70  per  cent,  remains  as  solid  residue  (coke)  in  the 
retort,  while  about  5 per  cent,  separates  as  tar  and  7 per  cent, 
as  tar  water  in  the  condensers  between  the  retort  and 
gasometer. 

o.  The  gas  itself  contains  many  NOXIOUS  INGREDIENTS, 
especially  sulphides  and  cyanides.  These  are  removed  by 
passing  the  gas  over  lime  and  basic  iron  sulphate.  These 
materials  become  offensive  when  dumped;  it  has  been  neces- 
sary to  work  them  up  for  sulphur  and  for  cyanogen  compounds. 
Thus  noxious  waste  products  have  been  made  profitable. 

6.  THE  COKE  left  in  the  retorts  is  larger  in  bulk  than  the 
coal  used;  it  is  a useful  fuel,  burning  (like  anthracite)  without 
flame,  but  containing  all  the  ashes  of  the  coal  used.  THE 
TAR  and  TAR-WATER  are  run  into  pits  where  the  two  liquids, 
separate.  The  most  valuable  constituent  of  the  tar-water  is 
ammonia;  it  is  converted  into  sulphate,  amounting  to  about 
one  per  cent,  of  the  coal  used. 

7.  THE  COAL  TAR  PRODUCED  in  the  gas  works  of  the 
world  amounts  to  over  a million  tons  a year.  Germany  and 
the  United  States  produce  over  one  hundred  thousand  tons 
each,  and  England  six  hundred  thousand  tons  a year.  It  is 
worked  up  mainly  for  coloring  and  disinfecting  materials. 
The  chemical  coal  tar  industry  is  most  highly  developed  in 
Germany. 

8.  The  crude  tar  is  first  subjected  to  FRACTIONAL  DIS- 
TILLATION. Four  fractions  are  taken  at  about  170,  230,  270 
degrees  and  above,  called  respectively  light  oil,  middle  oil, 
heavy  oil  and  anthracene  oil ; the  residual  black  pitch  is  drawn 
as  viscid  liquid  from  the  boiler.  Each  of  the  four  tar  oils  is 
subjected  to  further  fractioning  and  chemical  purifications. 

9.  In  this  way,  the  LIGHT  OIL  yields  mainly  benzol, 
toluol  and  naphta,  together  with  a very  small  per  cent,  of 


298 


LECTURE  73. 


pyridine.  The  MIDDLE  OIL  furnishes  mainly  phenol  and 
naphtalene.  The  HEAVY  OIL  gives  naphtols,  cresols  and 
liquid  paraffins.  The  ANTHRACENE  OIL  is  the  most  valuable 
fraction,  giving  fast  coloring  materials  (alizarin,  61.10) ; but 
its  amount  is  small. 

10.  The  purification  and  properties  of  the  most  important 
of  these  TAR  PRODUCTS  will  be  considered  in  another  lesson. 
The  graphical  representation  above  given  of  the  amount  of 
these  products,  compared  to  the  coal  taken,  is  due  to  Wurtz 
(1876).  The  piece  of  coal  (1)  represented  weighs  about  300 
grammes.  Tar,  2.  Tar  Oils:  light,  3;  middle  and  heavy,  4; 
green,  5.  Benzol,  6.  Toluol,  7.  Phenol,  8.  Naphtalene,  9. 
Anthracene,  10. 

11.  QUANTITATIVE  EXPERIMENTS  on  this  dry  distillation 
of  coal  are  made  by  heating  one  to  three  decigrammes  of  coal 
in  a glass  tube,  connected  with  a U-tube  (submerged  in 
water)  and  attached  to  a 100  cc.  gas  burette.  The  coke  remains 
in  the  combustion  tube,  the  tar  and  ammonia  water  are  found 
in  the  U-tube,  and  30  to  90  cc.  gas  collect  in  the  burette. 
The  illuminating  gas  weighs  about  half  a milligramme  per 
cubic  centimeter.  Air  containing  between  5 and  30  per  cent, 
of  the  gas  is  explosive;  most  violently  so  when  containing 
about  17  per  cent. 

12.  By  heating  ten  to  twenty  grammes  of  bituminous  coal 
in  a regular  combustion  tube,  the  tar  and  tar  water  will  show 
up  very  nicely,  and  the  gas  may  be  collected  in  a glass- 
gasometer  or  burnt  in  a gas  burner.  The  burners  of  the 
combination  furnace  nearest  the  U-tube  should,  of  course,  be 
lit  first;  the  others  are  turned  on  gradually  to  maintain  a 
steady  flow  of  illuminating  gas. 


74.  PHENOL  AND  ANILINE. 


1.  The  pure  chemical  compounds,  which,  by  means  of 
repeated  fractioning  and  washing  with  appropriate  solvents 
are  extracted  from  coal  tar  are  often  called  AROMATIC  COM- 
POUNDS. Of  these,  the  most  volatile  BENZOL,  has  already 
been  described  (62.6).  The  others  of  general  interest  will 
now  be  considered.  They  are  strongly  acted  upon  by  bromine 
and  by  nitric  acid. 

2.  NAPHTALENE  is  extracted  from  the  middle  tar  oil,  from 
which  it  crystallizes  upon  cooling;  it  is  purified  by  sub- 
limaiion.  When  pure  it,  forms  colorless  lamellar  crystals, 
retaining  a peculiar,  tar-like  odor,  and  having  a notable  vapor 
tension  even  at  15°.  F 79,  B 218.  Burns  with  very  fuliginous 
flame.  Insoluble  in  water,  soluble  in  alcohol,  ether  and  ben- 
zol. Moth  balls  and  tar  camphor  are  commercial  forms  of 
naphtalene. 

3.  ANTHRACENE  is  the  most  valuable  constituent  of  the 
crude  anthracene  oil  (green  oil)  coming  over  above  270°.  By 
hot  pressure  the  more  fusible  ingredients  are  removed.  The 
solid  residue  is  redistilled,  the  fraction  passing  over  between 
340  and  360  is  retained,  purified  by  solution  in  hot  benzol  and 
crystallization  on  cooling;  finally  it  is  sublimated.  It  forms, 
colorless,  rhomboidal  tablets;  F 210,  B 350.  Soluble  in  hot 
benzol,  difficultly  soluble  in  alcohol  and  ether,  insoluble  in 
water. 

4.  Benzol,  naphtalene  and  anthracene  are  NEUTRAL  SUB- 
STANCES, neither  acid  nor  alkaline,  insoluble  in  water.  The 
tar  oils  contain  a number  of  allied  neutral  bodies,  differing  in 
properties  from  the  type  compounds  given.  Thus  TOLUOL 
(B  111,  still  liquid  at  — 28)  remains  liquid  when  benzol 
crystallizes;  it  has  first  been  extracted  from  balsam  of  tolu. 

5.  PHENOL  (carbolic  or  phenic  acid)  is  extracted  from  the 
middle  tar  oil,  after  the  naphtalene  has  crystallized  out.  The 


300 


LECTURE  74. 


residue  is  shaken  with  sulphuric  acid  to  remove  alkaline 
bodies.  After  this  separation,  the  liquid  is  stirred  with  con- 
centrated caustic  soda  and  heated  by  steam,  forming  sodium 
phenate.  From  the  separated  pure  solution,  sulphuric  acid 
precipitates  crude  carbolic  acid,  this  being  but  slightly  soluble 
in  water.  It  is  washed,  dried  over  calcium  chloride,  and 
rectified.  The  liquid  cooled  to — 10°  deposits  crystals. 

6.  Pure  phenol  forms  needle-shaped,  colorless  crystals. 
G 2.06;  F 42;  B 182.5.  It  has  a burning  taste,  dissolves 
slowly  in  20  parts  of  water,  forming  a solution  not  acting  on 
litmus  paper,  nor  decomposing  alkaline  carbonates.  It  is 
soluble  in  hot  water,  alcohol,  ether,  glycerin,  fixed  oils,  fixed 
alkalies  and  ammonia;  very  caustic  on  skin  (Ka  bromide  best 
antidote).  It  is  strongly  antiseptic.  Ferric  chloride  colors  it 
violet,  even  in  dilute  solution.  Bromine  water  gives  a white 
precipitate. 

7.  Associated  with  phenol  are  the  CRESOLS,  which  are 
more  liquid  (F  6 to  over  40  below)  and  less  volatile  (B  from 
5 to  15  higher)  than  phenol.  They  are  more  strongly  anti- 
septic than  phenol,  and  thus  make  crude  phenol  much  more 
antiseptic  than  pure  phenol ; but  also  much  more  poisonous. 
The  most  liquid  cresol  is  the  strongest  in  this  regard;  it  is 
especially  abundant  in  the  tar  from  pine  and  beech  wood. 

8.  The  heavy  tar  oil  contains  two  closely  related  sub- 
stances distinguished  as  ALPHA  (a)  and  BETA  (/5)  NAPHTOL. 
Both  are  soluble  in  hot  water,  alcohol,  ether,  and  benzol; 
both  are  crystallized  solids,  and  smell  faintly  like  phenol. 
They  are  distinguished  by  the  following  characters.  «-Naphtol, 
most  poisonous,  silky  needles,  F 94,  B 278,  violet  with  ferric 
chloride;  ./^-Naphtol,  not  so  poisonous  (used  externally), 
pearly  scales,  F 123,  B 285,  greenish  with  ferric  chloride. 

9.  The  heavy  tar  oils  contain  also  minute  amounts  of  three 
remarkable  alkaline  bodies,  pyridine,  chinoline  and  aniline. 
They  are  taken  up  by  the  sulphuric  acid  used  in  the  process 
of  purifying  the  more  abundant  substances  described.  By 


PHENOL  AND  ANILINE. 


301 


super  saturation  of  these  acids  with  lime  and  distilling,  the 
TAR  BASES  are  obtained.  They  occur  in  much  larger  amount 
in  bone  oil,  from  which  they  are  therefore  more  generally 
obtained. 

10.  PYRIDINE  is  a colorless  liquid  with  penetrating,  char- 
acteristic odor,  miscible  with  water;  G 0.99  at  0°,  B 115. 

When  an  alcoholic  solution  of  pyridine  is  treated  with  a 
fragment  of  metallic  sodium,  the  liquid  assumes  the  odor  of 
pepper,  and  contains  the  new  alkaline  liquid  called  PIPER- 
IDINE (B  106)  forming  crystallizable  salts  with  acids. 

11.  CHINOLINE  is  a colorless,  strongly  refracting  liquid  of 
specific,  penetrant  odor.  G 1.095  at  20°,  B 239.  It  forms 
crystallizable  and  soluble  salts  with  acids;  its  bichromate  is 
difficultly  soluble,  and  forms  as  precipitate  in  sufficiently  con- 
centrated solutions.  Distilling  cinchona  bark  (or  its  alkaloid) 
quinine  with  caustic  potassa  yields  a distillate  containing 
chinoline;  hence  its  name. 

12.  ANILINE  is  a colorless,  oily  liquid,  turning  yellow  and 
finally  dark  brown  on  exposure  to  the  air.  Its  odor  is  weak, 
but  peculiar  and  unpleasant.  G 1.031,  B 149,  solidified  at — 8. 
Very  soluble  in  water  and  in  alcohol ; precipitates  many 
metals  (Zn,  Fe,  Al)  from  their  aqueous  solutions.  Chloride 
of  lime  colors  its  aqueous  solution  violet  purple.  Chromic 
acid  colors  it  first  red,  then  violet  and  finally  blue  in  the 
presence  of  strong  sulphuric  acid.  Potassium  bichromate  gives 
a dark  green  color,  burning  black.  Aniline  was  first  (1826) 
obtained  in  the  dry  distillation  of  indigo  (called  ANIL  in 
Spanish.)  It  is  the  basis  of  aniline  colors. 


75.  BONE  OIL  AND  WOOD  SPIRITS. 

1.  Exposing  an  organic  compound  in  a retort  to  a bright 
red  or  beginning  white  heat,  while  preventing  the  air  from 
access  to  the  same,  drives  off  all  that  is  volatile.  The  vapors 
liquefy  in  cooled  vessels  (condensers)  and  the  gases  are  col- 


302 


LECTURE  75. 


lected  in  gasometers.  Such  a process  is  called  DRY  DISTILLA- 
TION. The  products  obtained  are  four  in  kind:  solid  coke, 
liquid  tar  and  tar  water,  and  the  gas  mixture.  Lecture  73. 

2.  Evidently  the  same  material  will  give  DIFFERENT 
PRODUCTS  not  only  according  to  the  degree  of  heat  used,  but 
even  according  to  the  size  of  the  retort  and  the  readiness 
wherewith  the  products  can  escape  from  the  same.  The 
higher  the  temperature,  the  further  the  destruction  (decompo- 
sition) by  heat  will  be  carried.  In  a narrow  retort  with  narrow 
escape  opening,  the  products  will  be  exposed  longer  to  the 
decomposing  effects  of  the  heat  of  the  retort. 

3.  These  influences  are  well  understood  in  the  great 
industry  of  illuminating  gas.  To  obtain  RICH  ILLUMINATING 
GAS,  the  decomposition  must  not  be  carried  too  far.  High 
temperature,  a beginning  white  heat  (1200  to  1400°),  and 
large  openings  for  the  escape  of  the  gaseous  products  give  the 
best  illuminating  gas.  Lower  heat  gives  better  tar.  In 
merely  coking  the  coal  for  Iron  furnaces,  the  coke  must  be 
compact;  hence  the  coal  is  piled  high  enough  to  exert  pressure. 

4.  This  process  is  also  very  appropriately  called  DESTRUC- 
TIVE DISTILLATION.  All  vegetable  and  animal  substances 
give  the  four  kinds  of  products,  varying  in  proportion.  Thus 
animal  materials  give  strongly  ammonical  tar  water,  while 
wood  gives  acid  tar  water.  To  this  extent  destructive  distilla- 
tion furnishes  information  concerning  the  chemical  composition 
of  the  substance  used. 

5.  Each  of  the  four  products  obtained  is  again  VERY  COM- 
PLEX, as  has  been  sufficiently  shown  in  the  study  of  the  dry 
distillation  of  coal.  The  composition  of  the  gas,  and  especially 
that  of  the  tar,  is  extraordinarily  complex,  for  a great  many 
chemical  substances  can  be  extracted  therefrom  by  appropriate 
methods. 

6.  We  cannot  give  detailed  attention  to  this  interesting 
and  difficult  analytical  process.  But  in  presenting  an  outline 
of  the  dry  distillation  of  WOOD,  BONES  and  SHALES  we  not 


BONE  OIL  AND  WOOD  SPIRITS. 


303 


only  shall  obtain  important  compounds  from  these  prime  ma- 
terials, but  also  throw  considerable  light  on  the  question  raised. 
The  products  obtained  strikingly  represent  the  material  used. 

7.  BONES  are  subjected  to  dry  distillation  in  the  manu- 
facture of  Boneblack  or  animal  charcoal  (69,  11).  The  famous 
DippePs  Oil  is  rich  in  the  alkaline  bodies  pyridine  and  chino- 
line  (74,  9-11)  to  which  it  mainly  owes  its  medicinal  effects. 
The  animal  oils  of  earlier  chemists— such  as  the  OIL  OF 
VIPERS,  distilled  from  live  vipers — contained  the  same  bases. 
(Lemery,  edition  Baron,  pp.  669-674;  Paris  1757). 

8.  WOOD  yields  upon  dry  distillation  a strongly  acid  dis- 
tillate. Much  of  the  acetic  acid  of  the  market  is  obtained  by 
this  process.  The  highest  amount  of  acid  is  obtained  at  low 
temperature,  not  exceeding  400°.  The  charcoal  left  in  this 
case  is  brownish,  its  temperature  of  ignition  is  correspondingly 
low.  Beech  wood  yields,  per  hundred,  about  25  charcoal,  5 
tar,  45  crude  wood  vinegar  and  25  of  gas.  The  tar  from 
beech  wood  is  specially  rich  in  CREOSOT,  the  meat  preserva- 
tive of  smoke.  Creosot  concentrated  and  purified  is  called 
guajacol  (G  1.12,  B 201).  Bituminous  SHALES  give  largely 
paraffins  and  the  so  called  solar-oil. 

9.  the  principal  constituents  of  the  tar  water  from 
wood  are  pyroligneous  or  acetic  acid  (B  118),  wood  spirits 
(B  66)  and  aceton  (B  56).  Saturating  with  milk  of  lime  pre- 
cipitates the  acid  as  calcium  acetate,  from  which  the  liquid  is 
distilled  off.  Redistilling  with  chloride  of  lime  converts  the 
acetone  into  chloroform  (B  61),  which  passes  over  first;  the 
almost  pure  wood  spirits  (methyl  alcohol)  is  collected  above  66°. 

10.  Distilling  the  CALCIUM  ACETATE  with  concentrated 
muriatic  acid  gives  ACETIC  ACID,  which  is  purified  by  distil- 
lation with  potassium  bichromate  in  silver  retorts.  The  use  of 
sulphuric::  instead  of  muriatic  acid  is  objectionable,  since  gypsum 
precipitates,  and  organic  substances  present  reduce  the 
sulphuric  to  sulphurous  acid,  which  distills  over  with  the  acetic 
acid  from  which  it  is  difficultly  removed. 


304 


LECTURE  70. 


11.  ACETIC  ACID,  in  its  most  concentrated  form  (glacial), 
solidifies  at  17 ; B 118.  G 1.08  at  0°.  It  has  a characteristic, 
suffocating  odor,  and  a strong  acid  taste;  it  is  very  corrosive. 
It  dissolves  many  metals,  forms  salts  (acetates)  which  are 
almost  all  soluble.  It  is  the  oldest  acid  known. 

Forming  by  oxidation  of  alcohol,  its  lead  and  copper  salts 
were  made  in  antiquity  by  covering  the  metals  with  the  residue 
drawn  from  the  wine  press.  71,  8. 

12.  Methyl  alcohol  is  a colorless,  limpid  liquid  of  a 
pleasant  ethereal  odor.  G 0.81,  F — 134,  B 66.5.  Miscible 
with  water,  alcohol  and  ether,  and  as  solvent  generally  as 
effective  as  alcohol. 

ACETONE  is  a colorless  liquid  of  ethereal  odor,  G 0.81, 
B 56,  soluble  in  water,  alcohol  and  ether.  With  sodium 
bisulphite  it  forms  a crystalline  compound. 

CHLOROFORM  is  a colorless  liquid  of  pleasant,  character- 
istic odor,  hardly  soluble  in  water,  miscible  with  alcohol  and 
ether,  G 1.48,  F — 70,  B 61.  We  shall  soon  study  these 
substances  more  in  detail. 


76.  STARCH,  SUGAR  AND  GLUCOSE. 

1.  The  principal  prime  materials  of  the  organic  world  have 
now  been  considered.  It  has  also  been  shown  how  DEFINITE 
CHEMICAL  COMPOUNDS  have  been  extracted  from  these — 
many  thereof  having  been  in  use  since  antiquity.  It  will  next 
be  necessary  to  consider  some  of  the  CHEMICAL  CHANGES 
of  these  leading  organic  compounds. 

2.  The  sweet  principle  of  the  cane  (sucrose)  and  of  the 
grape  (glucose)  we  considered  in  the  first  lesson  (58)  of  our 
organic  chemistry;  the  most  important  cellular  substance, 
starch,  was  considered  later  on  (66).  We  shall  now  show 
how  both  starch  and  sucrose  are  readily  CONVERTED  INTO 
GLUCOSE  by  simple  chemical  means. 


STARCH,  SUGAR  AND  GLUCOSE. 


305 


3.  Starch,  thoroughly  wet  by  rubbing  with  a little  water, 
then  boiled  with  much  water,  gives  starch  paste  (66,  10) ; 
when  cold,  this  gives  the  delicate  iodine  reaction  (blue).  But 
if  a little  dilute  sulphuric  acid  be  added  to  the  boiling  starch 
paste,  this  will  gradually  get  thin.  If  the  boiling  is  stopped 
while  the  liquid  still  is  sticky,  it  gives  a precipitate  with 
alcohol,  but  no  blue  with  iodine.  The  starch  has  been  con- 
verted into  DEXTRINE. 

4.  If  the  boiling  continues,  the  starch  solution  will  finally 
cease  to  be  sticky,  and  give  no  longer  a precipitate  with 
alcohol.  If  the  acid  is  now  neutralized  (say  by  adding  a 
slight  excess  of  powdered  chalk),  the  solution  will  give  the 
glucose  reaction  (58,  6).  Accordingly  the  STARCH  HAS  BEEN 
CONVERTED  INTO  GLUCOSE.  Dilute  muriatic  acid  (1  per 
cent.)  effects  the  conversion  more  completely. 

5.  The  roots  of  most  composite  (Inula  helenium.  Dahlia, 
Helianthus,  Taraxacum,  etc.)  contain  a pseudo-crystalline  sub- 
stance, soluble  in  water,  precipitable  by  alcohol,  tinted  yellow 
by  iodine,  called  INULIN,  and  considered  to  take  the  place  of 
starch.  It  rather  seems  to  correspond  to  amidine  (66.10) 
and  may,  therefore,  be  called  levulin;  for  boiled  with  dilute 
acids  it  yields  a glucose,  deporting  itself  chemically  exactly 
as  the  glucose  made  from  true  starch. 

6.  Physically  the  glucose  from  starch  and  from  inulin  act 
in  almost  opposite  manner  on  polarized  light.  The  solution 
fulled  into  a brass  tube  (10  or  20  cm.  long),  closed  with  plane 
plate  glass  at  the  ends,  turns  the  plane  of  polarization  of  light 
to  the  RIGHT  in  the  case  of  glucose  from  starch,  to  the  LEFT 
in  case  of  glucose  from  inulin.  These  two  forms  of  glucose, 
accordingly,  are  called  DEXTROSE  and  LEVULOSE. 

7.  HONEY  contains  both  kinds  of  glucose,  namely,  dextrose 
and  levulose.  By  stirring  up  honey  in  cold  alcohol,  only  the 
levulose  is  dissolved ; the  dextrose  is  separated  by  filtration 
and  pressure,  and  can  be  dissolved  in  boiling  alcohol,  from 
which  it  will  crystallize  upon  cooling. 


306 


LECTURE  76. 


8.  Sucrose  dissolved  in  water,  very  slowly  changes  into  a 
mixture  of  levulose  and  dextrose,  called  INVERT-SUGAR.  By 
heating,  the  process  is  accelerated.  It  is  quite  prompt  when 
sucrose  is  boiled  with  dilute  acid;  the  boiled  solution,  after 
neutralization,  will  exhibit  the  glucose  reaction  with  Fehling’s 
solution.  Sugar  boiled  with  fruit  (acid  juice)  is  also  inverted; 
hence  in  putting  up  fruit,  sucrose  ought  to  be  added  last. 

9.  Sucrose  solutions  do  not  ferment;  syrups  keep  quite 
well.  But  all  forms  of  GLUCOSE  FERMENT  promptly.  Hence 
starch  sugar  is  made  on  a commercial  scale  (from  potato  starch 
in  Germany,  from  corn  starch  in  the  United  States)  and  some 
finds  its  way  to  breweries,  acetic  acid  works,  and  even  to 
other  factories. 

10.  Claude  Bernard  (p.  36)  discovered  (1856)  animal 
starch  (GLYCOGEN)  in  the  liver,  and  in  oysters.  The  latter 
may  be  crushed  in  a mortar,  and  thrown  into  boiling  water;  if 
to  the  cold,  opaline  filtrate,  a large  amount  of  alcohol  (or 
glacial  acetic  acid)  is  added,  the  glucogen  separates  as  a 
white,  amorphous  powder.  It  is  changed  into  glucose  (dex- 
trose) exactly  as  is  starch. 

11.  All  farinaceous  food  consists  largely  of  starch,  which 
can  only  enter  the  blood  in  soluble  form,  as  glucose.  The 
liver  evidently  takes  a prominent  part  in  effecting  this  change. 
In  a normal  state  (health)  this  glucose  is  used  in  the  system 
(assimilated).  In  DIABETES  MELLITUS,  large  amounts  of  glu- 
cose are  drained  from  the  system  in  the  kidneys.  The  urine  be- 
comes exceedingly  abundant  in  volume,  high  in  specific  gravity 
(1.035)  and  gives  the  glucose  reaction  with  Fehling’s  solution. 

12.  Cellulose,  by  protracted  boiling  with  dilute  acids,  can 
also  be  converted  into  glucose  (SUGAR  OF  RAGS)  ; more 
rapidly  if  the  acid  is  stronger,  when  much  material  is  lost^  by 
charing.  Fusing  cellulose  with  caustic  potash,  or  boiling 
sugar,  glucose  or  starch  with  rather  strong  nitric  acid,  yields 
OXALIC  ACID  (63,  10)  as  the  common  oxidation  product. 
From  the  nitric  acid  it  separates  on  cooling  in  crystal  form. 


STARCH,  SUGAR  AND  GLUCOSE. 


307 


Notes. — Gum  Arakic  is  an  exudation  from  species  of  acacia  and 
mimosa  in  northern  Africa  and  the  Orient.  It  is  colorless,  soluble  in 
water,  insoluble  in  alcohol,  like  dextrine,  which  latter  is  accordingly 
often  called  British  Gum.  In  that  case  dextrine  has  commonly  been 
manufactured  by  moistening  a ton  of  starch  with  300  kgr.  of  water,  to 
which  2 kgr.  of  common  nitric  acid  had  been  added.  The  mass,  after 
being  air  dried,  is  heated,  in  thin  layers,  to  100  ; in  about  an  hour  or 
two  it  has  changed  to  dextrine. 

Gum  Arabic  solution,  boiled  with  dilute  acid,  yields  a glucose 
(arabinose),  precisely  as  does  dextrine. 

Mucilage  is  extracted  by  boiling  water  from  linseeds  and  other 
materials.  Mucilages  resemble  gums. 

Pectine  dissolves  in  hot  water  and  gelatinizes  on  cooling.  It  is  pre- 
cipitated by  absolute  alcohol  from  certain  fruit  juices  (black  currants, 
etc.),  after  having  removed  lime  by  oxalic  acid  and  albuminoid  sub- 
stances bv  tannin. 


77.  ALCOHOL  AND  ETHERS. 

1.  The  extraction  of  alcohol  from  wines  has  been  shown 
(58,  11),  and  its  industrial  production  mentioned  (58,  12). 
We  have  also  seen  how  dilute  alcohol  is  converted  into  an  acid 
(71,  8)  and  how  this  acetic  acid  is  industrially  obtained 
(75,  11)  in  concentrated  form.  Dilute  acetic  acid,  obtained 
from  alcoholic  liquids,  is  called  VINEGAR,  and  is  used  in  the 
preparation  of  food  and  at  table;  it  retains  the  flavor  of  its 
origin. 

2.  If  to  a little  water  in  a test  tube  is  added  at  least  an 
equal  volume  of  concentrated  sulphuric  acid,  the  mixture  will 
be  quite  hot.  If  now  a few  drops  of  alcohol  be  added,  the 
pleasant  odor  of  ETHER  will  be  noticed.  If  a crystal  of  any 
acetate  be  dropped  into  this  liquid,  the  more  fragrant  odor  of 
ACETIC  ETHER  will  be  recognized.  Compare  55.12.  Such 
effects  have  already  been  observed  by  the  alchemists;  Lully 
in  the  13th,  Valentin  in  the  15th  century. 

3.  This  simple  test  shows  how  common  and  compound 
ethers  are  obtained,  namely  by  distilling  alcohol  with  much 


308 


LECTURE  77. 


sulphuric  acid  alone  and  with  some  organic  or  other  acid. 
The  ether,  being  very  volatile  QUITE  INFLAMMABLE,  and 
forming  explosive  mixtures  with  air,  this  distillation  must 
be  made  with  great  care,  and  by  experienced  operators  only. 
In  ether  factories,  all  heating  is  done  by  steam  carried  from 
another  building,  so  that  no  fire  nor  flame  is  allowed  in  the 
building  where  ethers  are  made. 

4.  To  obtain  COMMON  ETHER  (so-called  sulphuric  ether) 
200  gr.  of  sulphuric  acid  are  mixed  with  120  gr.  alcohol,  and 
the  mixture  distilled  at  140  to  145  degrees.  By  a special  con- 
trivance, a continuous,  though  small  flow  of  alcohol,  correspond- 
ing to  the  ether  distilled  over,  may  be  kept  up  till  the  acid 
becomes  inert  when  too  dilute  from  water  formed  in  the 
process.  The  receiver  must  be  well  cooled. — The  ether  formed 
contains  no  sulphuric  acid. 

5.  The  CRUDE  ETHER  so  obtained  is  treated  with  milk  of 
lime  for  a day,  and  frequently  agitated  therewith;  this 
removes  the  acid  that  has  passed  over.  The  ether  is  next 
washed  with  water,  dried  on  calcium  chloride,  and  finally 
rectified  over  metallic  sodium  on  the  water  bath,  if  the  last 
traces  of  water  and  alcohol  are  to  be  removed. 

6.  Pure  ether  is  a very  limpid,  colorless  liquid  of  a 
strong,  characteristic  and  pleasant  odor,  and  a sharp,  burning 
taste.  G 0.75  at  0,  B 34.5;  it  solidifies  to  crystalline  scales 
at — 31.  It  is  non-miscible  with  water,  on  which  it  floats.  It 
mixes  with  alcohol  in  all  proportions.  Water  dissolves,  upon 
shaking,  about  one-tenth  its  own  volume  of  ether.  Ether  is 
a most  important  solvent  (S,  P,  lo)  especially  for  fats  and  oils. 
Very  combustible  and  inflammable,  see  above  (3). 

7.  By  distilling  a mixture  of  (fused)  sodium  acetate,  alcohol 
and  sulphuric  acid  in  the  proportions  of  10,  6,  15,  crude 
ACETIC  ETHER  is  obtained.  It  is  purified  by  shaking  with 
milk  of  lime  and  rectification  from  calcium  chloride.  G 0.91 
at  0,  B 74;  water  dissolves  one-seventh  its  own  volume  ; mixes 
with  alcohol  in  any  proportion.  It  is  a solvent  of  resins  and 


ALCOHOL  AND  ETHERS. 


300 


gun  cotton.  Wine  and  wine  vinegar  contain  a sufficient 
amount  of  this  ether  to  be  recognized  by  the  very  character- 
istic odor, 

8.  When  acetic  ether  is  treated  with  sodium  hydrate, 
alcohol  reappears,  and  can  be  distilled  off;  the  solid  residue 
is  sodium  acetate.  Thus  the  original  substances  are  repro- 
duced; the  REACTION  HAS  BEEN  REVERSED.  Consequently 
alcohol  must  be  a hydrate  of  some  radical,  passing  into  the 
ether  by  mere  double  decomposition.  Liebig  (p.  23)  called 
this  radical  ETHYL,  symbol  Et. 

9.  The  reactions  involved  are  all  DOUBLE  DECOMPOSI- 
TIONS. In  the  formation,  Na  Ac^te  and  Et  H^te  (alcohol)  give 
the  volatile  Et  Ac^te  (acetic  ether)  and  Na  H^te  in  presence  of 
excess  of  heated  strong  sulphuric  acid,  which  forms  Na 
and  absorbs  H H^te  (water).  When  the  acetic  ether  is  treated 
with  Na  Hate  at  common  temperatures,  alcohol  (Et  Hate)  and 
Na  Acate  reform;  the  first  can  be  distilled  off,  the  latter 
remains  as  salt. 

The  formation  of  common  ether  now  is  readily  understood. 
Alcohol,  as  ethyl  hydrate,  Et  OH,  in  contact  with  the  hot, 
concentrated,  hygroscopic  sulphuric  acid,  gives  off  water  and 
becomes  ether  or  ethyl  oxide,  Et2  O.  Two  alcohol  give  one 
each  of  water  and  ether,  namely  2 Et  OH  give  Ha  O and 
Et2  O. 

10.  Many  other  ethers  are  distilled  in  a like  manner  from 
alcohol  and  the  salt  in  presence  of  an  excess  of  strong  sul- 
phuric acid.  Thus  common  salt  (Na  CL^e)  yields  CHLORIC 
ETHER.  Heating  chloric  ether  with  water  in  a covered  vessel 
under  moderate  pressure  gives  alcohol  and  muriatic  acid. 
This  double  decomposition  again  shows  that  alcohol  is  ethyl 
hydrate. 

11.  When,  however,  strong  muriatic  acid  (H  Cf^^)  and 
alcohol  (Et  Hate)  are  heated  in  an  AUTOCLAVE  (28,  3-4)  up 
to  140°,  or  under  a pressure  of  40  atmospheres,  chloric  ether 
(Et  ClUe)  and  water  (H  Hate)  are  formed  by  double  decom- 


310 


LECTURE  78. 


position.  This  reversible  reaction  again  confirms  the  consti- 
tution of  alcohol  as  ethyl  hydrate.  Under  40  atmospheres  the 
reaction  is  the  reverse  of  that  under  one  or  two  atmospheres. 
The  ether  Et  Chde^  boils  at  11  degrees.  It  is  sold  in  strong, 
sealed  glass  tubes  and  used  as  a local  anesthetic. 

12.  Taking  potassium  nitrite — and  better  strong  muriatic, 
instead  of  sulphuric  acid — NITROUS  ETHER  is  obtained, 
which  as  5%  solution  in  alcohol  is  a valuable  remedy,  called 
sweet  spirits  of  nitre.  Also  this  reaction  is  reversed;  for 
potassium  hydrate  added  to  the  nitrous  ether  gives  again 
potassium  nitrite  and  alcohol.  Thus  the  ethyl  radical  forms 
alcohol  with  H^te,  and  ethers  with  acid  radicals.  Nitrous 
ether  boils  at  17°. 


78.  FATS  AND  SOAPS. 

1.  Oil  and  water  do  not  mix.  By  shaking,  temporary 
emulsion  may  be  obtained,  which  soon  separates  again  in  the 
two  layers  of  water  and  oil.  But  if  an  alkali  is  dissolved  in 
the  water,  and  the  mixture  gently  heated,  complete  solution 
is  affected;  a SOAP  is  produced.  This  solution  of  a fat  in  an 
alkaline  aqueous  liquid  is  called  SAPONIFICATION. 

2.  Wood  ashes  used  instead  of  caustic  alkali  effect  an 
incomplete  solution  only.  The  Gauls,  according  to  Pliny, 
operated  in  this  manner.  In  modern  times  the  cheapening  of 
the  process  has  made  soap  available  to  everybody.  England 
produced  in  1791  twenty  thousand  tons  of  soap,  worth  eight 
million  dollars;  ninety  years  later,  it  produced  eight  times  as 
much,  costing  only  a little  more  than  twice  as  much  (eighteen 
million  dollars).  Industrial  progress  had  brought  the  price 
down  to  one -fourth. 

3.  Alkalies  are  not  the  only  substances  that  make  oil  dis- 
solve in  water  on  moderate  heating.  Litharge  has  a corres- 


FATS  AND  SOAPS. 


;ui 


ponding  effect;  the  product,  called  PLASTER,  differs  from 
ordinary  soaps.  The  great  chemist,  Scheele  (p.  169),  repeat- 
ing this  process  in  his  little  pharmacy  in  Sweden,  discovered 
1779  the  “sweet  principle  of  oils,”  which  we  now  call 
GLYCERIN,  in  the  aqueous  liquid  remaining  when  the  plaster 
is  finished. 

4.  Chevreul  (p.  37)  completed  the  PROXIMATE  CHEMI- 
CAL ANALYSIS  OF  THE  FATS  as  early  as  1815,  mainly  by  a 
chemical  examination  of  the  old  process  of  saponification.  Fie 
first  separated  the  natural  fats  into  simple  fats  (59.9)  such  as 
olein,  stearin.  Fie  next  found  that  each  simple  fat,  in  saponi- 
fication, really  undergoes  a double  decomposition  with  the 
caustic  alkali  (hydrate).  Consequently,  FATS  ARE  SALTS 
(OR  ETHERS).  Glycerin  is  the  common  base  of  all  fats. 

5.  Thus,  stearin  is  glyceryl  stearate,  if  the  radical  of 
glycerin  be  denoted  according  to  Liebig’s  system  (yl).  With 
caustic  potassa  (potassium  hydrate)  on  boiling,  double  decompo- 
sition takes  place.  Soap  is  formed,  that  is  potassium  stearate 
(soft  soap).  Glycerin,  accordingly,  must  be  GLYCERYL 
HYDRATE.  If  salt  is  thrown  into  this  soap  solution,  sodium 
stearate  (hard  soap)  separates,  being  much  less  soluble  than 
soft  soap. 

6.  Chevreul  dissolved  four  parts  of  fat  in  two  parts  of 
water  containing  one  part  of  caustic  potassa.  The  solution 
was  effected  on  the  water  bath.  When  complete,  he  dilutes 
with  water  and  adds  just  enough  tartaric  acid  to  neutralize  the 
potassa;  THE  FATTY  ACID,  being  insoluble  in  water,  sepa- 
rates on  cooling,  forming  an  oily  layer  or  a solid  cake.  By 
washing  with  water  this  acid  is  purified. 

7.  THE  REACTION  involved  is  again  merely  a double 
decomposition.  Soap  from  stearine  by  caustic  potassa  is 
potassiurn  stearate.  Adding  to  its  aqueous  solution  hydrogen 
tartrate  gives  potassium  tartrate  (difficultly  soluble)  and 
hydrogen  stearate  or  stearic  acid,  insoluble  in  water.  On  the 
hot  solution  this  acid  forms  an  oily  layer,  which  solidifies  to 


312 


LECTURE  78. 


a fatty  cake  on  cooling.  Palmitic  acid  appears  in  the  same 
form.  Oleic  and  butyric  acids  are  liquid  at  common  tempera- 
tures. The  last  is  volatile  and  can  be  distilled  off. 

8.  These  fatty  acids  are  soluble  in  alcohol  and  ether, 
from  which  they  crystallize  below  their  melting  point.  This 
is,  for  stearic  acid  69,  palmitic  acid  62,  oleic  acid  14.  Butyric 
acid  solidifies  below  the  freezing  point  and  boils  at  163.  The 
other  fatty  acids  named,  when  heated,  decompose  before 
boiling.  With  steam  they  volatilize,  like  many  volatile  oils 
(60,  3).  The  so-called  stearin  candles  consist  mainly  of 
stearic  acid  and  not  of  stearin. 

9.  It  is  evident  that  a mixture  of  fatty  acids  can  be  more 
readily  separated  than  the  corresponding  mixture  of  the  fats. 
Accordingly,  saponification  is  generally  resorted  to  in  THE 
ANALYSIS  OF  FATS.  Butyric  acid  is  distilled  off.  Oleic 
acid  decanted  and  pressed  from  the  solids.  The  amount  of 
potassa  (in  mgr.  per  gramme  of  fat)  required  for  saponification 
(Koettstorfer’s  number)  is  determined  by  difference.  The 
amount  distilled  off  is  determined  by  tenth -normal  alkali;  the 
number  of  cc  required  for  5 grammes  of  fat  is  called  Reichert’s 
number.  It  is  most  important  in  testing  butter. 

10.  The  soap  and  stearine  candle  industries  have  flourished 
especially  in  France,  where  the  principal  chemical  investiga- 
tions of  the  fats  have  been  made.  The  soap  industry  at  Mar- 
seilles is  the  most  extended  and  oldest  in  the  world;  it  is  the 
commercial  center  of  the  olive  oil  region.  Genuine  castile 
soap  is  made  from  this  oil.  France  excells  also  in  toilet  soaps, 
on  account  of  the  perfumes  required  (60,  5-7). 

11.  The  DIRECT  DECOMPOSITION  OF  FATS  into  acid  and 
glycerine  is  effected  by  high  pressure  steam  (10  atmospheres) . 
After  several  hours’  action,  the  glycerin  is  dissolved  in  the 
water  while  the  fatty  acids,  floating  on  the  surface,  are  blown 
over  with  the  steam.  The  glycerin  so  obtained  is  the  purest 
in  the  market.  This  process  is  largely  employed  in  England 
and  in  the  United  States. 


FATS  AND  SOAPS. 


313 


12.  The  direct  SYNTHESIS  OF  FATS  from  their  constituents, 
acid  and  glycerin,  has  been  effected  (in  ISoT)  by  Berthelot 
(p.  27).  It  takes  place  at  common  temperatures  to  a very 
slight  extent  in  a very  long  time.  It  is  quite  slow  even  at 
100  degrees.  In  the  autoclave,  at  200  degrees  (or  about  16 
atmospheres)  Berthelot  effected  the  synthesis  in  a few  hours, 
in  three  distinct  stages,  (proving  that  glycerin  is  a tri -valent 
base  43,  11).  Here  we  have  witnessed  another  most  remark- 
able reversible  reaction. 


79.  NITROGLYCERIN  AND  GUN-COTTON. 

1.  Man  alone  has  not  been  endowed  with  special  ORGANS 
OF  DEFENSE,  nor  is  he  swift  enough  to  escape.  But  intelli- 
gence has  armed  his  hand,  and  courage  needs  no  wings  to 
flee.  Thus  primitive  man  conquered  the  animal  world  in  the 
golden  age,  with  stone  and  bow,  with  ax  and  spear. 

2.  In  his  contests  for  dominion,  man  depended  for  ages  on 
the  strength  of  his  own  MUSCLE.  The  armies  of  the  Romans, 
and  of  the  Saracen  and  Christian  Knights  during  the  Crusades, 
exhibit  this  phase  of  man  in  its  highest  form.  When  cunning 
and  over- confidence  decide  the  contest,  as  at  Troy,  we  feel 
sympathy  neither  for  the  victor  nor  for  the  vanquished. 

3.  About  equally  remote  in  time,  the  contest  between 
David  and  Goliath  foreshadows  the  contrast  between  modern 
and  ancient  arms.  Reading  the  dramatic  account  in  the  Scrip- 
tures (I  Samuel  17)  one  is  fascinated  by  the  parallel.  Goliath, 
proud  of  his  muscle ; David,  frail  youth,  conquers  by  MECHANI- 
CAL SKILL,  long  before  the  arm  of  the  giant  can  reach  him. 

4.  THE  EXPLOSIVES,  furnished  by  chemistry,  have  en- 
dowed the  modern  soldier  with  a power  incomparably  greater 
than  his  own  muscular  strength.  The  introduction  of  the 
crude  black  powder  changed  the  condition  of  man ; serfdom 
was  doomed  when  the  blunderbuss  took  the  place  of  the  spear. 


314 


LECTURE  79. 


During  the  half  century  now  closing,  CHEMISTRY  HAS  AGAIN 
GREATLY  ENLARGED  THE  RANGE  AND  POWER  OF  THE 
INDIVIDUAL;  we  may  hope  it  will  lift  the  burden  of  militaiism 
from  the  race. 

5.  In  BLACK  POWDER  or  gun-powder,  we  have  a MIXTURE 
of  two  combustible  substances  (C  and  S)  with  a sufficiency 
of  nitre  to  furnish  the  oxygen  to  completely  burn  them  (21, 12). 
A spark  is  sufficient  to  start  the  combustion.  This  suddenly 
converts  the  small  amount  of  solid  powder  into  a very  large 
volume  of  hot  gas.  The  pressure  thus  produced  is  about  two 
thousand  atmospheres.  The  projectile  is  thrown,  or  the  rock 
Is  broken  by  the  force  of  such  an  explosion. 

6.  The  modern  chemical  explosives  (nitroglycerin,  gun- 
cotton, smokeless  powder)  are  not  explosive  mixtures,  but 
essentially  EXPLOSIVE  COMPOUNDS.  The  combustible 
materials  (C,  H)  are  in  atomic  proximity  to  the  oxygen  of  the 
compound.  The  action  is  therefore  instantaneous,  so  much  so 
that  the  air  acts  like  a resistant  solid.  A drop  of  nitro- 
glycerin, exploding  on  a hard  steel  plate,  knocks  a hole  into 
the  same— the  air  acting  like  the  sand  tamping  in  a blast  hole 
charged  with  black  powder. 

7.  The  work  of  the  last  fifty  years  has  therefore  been 
mainly  directed  to  find  means  to  TEMPER  THE  VIOLENCE  of 
these  modern  explosives.  Schoenbein,  in  Germany,  dis- 
covered gun-cotton  (1846),  Sobrero,  of  Turin  (1847)  nitro- 
glycerin. Ncbel,  of  Sweden,  tempered  the  later  in  dynamite 
(1867),  which  ever  since  has  done  man’s  work  in  mine,  quarry 
and  tunnel.  Turpin  and  Vieille,  of  France,  in  1888  made  the 
first  practical  smokeless  powder.  The  three  steps  taken  are 
about  twenty  years  apart  in  time. 

8.  NITROGLYCERIN  is  made  by  pouring  glycerin  into  a 
cold  mixture  of  concentrated  nitric  (3)  and  sulphuric  acid  (5  parts 
per  unit  of  glycerin).  The  nitroglycerin  (G  1.60),  floating  on 
the  cooled,  acid  mixture,  is  separated  and  washed  with  water 
and  soda  solution.  It  is  sweetish.  Being  extremely  explosive, 


NITROGLYCERIN  AND  GUN-COTTON. 


315 


it  is  not  accepted  for  transportation  in  most  countries.  By  a 
blow  or  concussion  it  explodes  instantaneously;  small  amounts 
burn  quietly  in  an  open  vessel.  Its  products  of  combustion 
are  carbon  dioxide,  water,  nitrogen  and  a slight  excess  of 
oxygen. 

9.  Nitroglycerin  is  an  ether,  corresponding  to  the  original 
fat  itself;  namely  GLYCERYL  NITRATE.  For  when  treated 
with  caustic  potassa  it  yields,  by  double  decomposition,  potas- 
sium nitrate  and  glyceryl  hydrate  or  glycerin.  The  sulphuric 
acid  simply  takes  up  the  water  in  the  process.  Nitroglycerin 
is  absorbed  by  infusorial  earth  in  the  proportion  of  three  to  one. 
The  mixture  called  DYNAMITE,  feels  dry,  is  reasonably  safe, 
accepted  for  transportation  under  proper  restrictions,  and  has 
for  a quarter  of  a century  been  the  most  effective  industrial 
explosive. 

10.  Cotton  soaked  in  the  same  acid  mixture  is  converted 
into  GUN-COTTON.  If  the  mixture  is  less  concentrated, 
PYROXYLIN  results.  The  first  contains  about  14  per  cent,  of 
nitrogen,  the  latter  only  11.  A solution  of  ferrous  sulphate 
in  concentrated  muriatic  acid  decomposes  either  with  evolution 
of  nitric  oxide  gas;  the  volume  of  which,  determined  by  the 
gas  burette,  gives  the  per  cent,  of  nitrogen  introduced. 
Pyroxylin  is  soluble  in  a mixture  of  alcohol  and  ether;  the 
solution,  on  spontaneous  evaporation, .leaves  a film  of  collodion. 
Gun-cotton  is  not  soluble. 

11.  While  not  soluble  in  any  solvent,  true  gun-cotton 
gelatinizes  with  acetic  ether  and  with  acetone,  especially  upon 
the  addition  of  a little  camphor.  SMOKELESS  POWDER  is 
mainly  such  gelatinized  gun-cotton  and  pyroxylin,  of  about  13 
per  cent,  nitrogen.  It  is  rolled  into  plates,  cut  into  small 
squares,  which  are  lightly  covered  with  graphite.  Giving  no 
solid  product,  its  explosion  gives  no  smoke,  only  a light  cloud 
of  watery  vapor. 

12.  To  explode  either  black  or  smokeless  powder,  MER- 
'CURIC  FULMINATE  caps  are  used.  It  is  made  by  adding 


316 


LECTURE  80. 


alcohol  to  a solution  of  mercuric  nitrate.  The  process  is  very 
dangerous,  therefore  the  particulars  need  not  be  given. 

With  cannon  hurling  a ton  weight  ten  miles,  rapid  firing 
guns  able  to  kill  a hundred  men  a minute,  and  torpedoes  that 
will  blow  up  a five-million-dollar  iron  clad  in  an  instant,  we 
may  hope  that  attack  will  soon  be  useless. 


80.  CHLORACETIC  ACID  AND  CHLORAL. 

1.  In  the  four  preceding  lessons  a number  of  chemical' 
changes  of  organic  compounds  have  been  presented.  In  no 
case  have  we  noticed  any  chemical  reaction  other  than  those 
common  to  inorganic  chemistry  (see  Lecture  28).  Thus  far, 
most  processes  involved  a DOUBLE  DECOMPOSITION.  It 
will  be  advisable  to  select  also  a few  striking  instances  of 
substitution. 

2.  As  far  back  as  1815,  Gay-Lussac  noticed  that  wax, 
bleached  with  chlorine  gas,  absorbed  some  thereof  without 
change  of  volume  in  the  gas.  Faraday,  in  1824,  and  Liebig 
and  Bunsen,  in  1832  discovered  similar  cases  of  SUBSTITU- 
TION OF  CHLORINE  FOR  HYDROGEN  in  organic  compounds. 
Soon  after  (1834)  Dumas  made  this  a subject  of  transcendent 
chemical  importance. 

3.  In  1840,  Dumas  changed  acetic  acid  into  TRI -CHLORA- 
CETIC ACID  by  simple  substitution.  Large,  dry,  glass 
stoppered  flasks  were  filled  with  dry  chlorine  gas.  A small 
amount  of  glacial  acetic  acid  was  introduced  into  each;  only  9 
decigrammes  per  liter.  Exposed  to  bright  sunshine,  the  walls 
of  these  flasks  soon  were  covered  with  small,  colorless,  crystals 
of  (tri- )chloracetic  acid. 

4.  In  this  process  there  is  NO  CHANGE  IN  VOLUME  of 
the  gas,  neither  increase  nor  diminution.  Accordingly,  hydro- 
gen and  chlorine  replace  one  another  in  equal  measures,  or 


CHLORACETIC  ACID  AND  CHLORAL. 


317 


equivalent  for  equivalent.  Therefore  MH,  the  organic  com- 
pound, and  Cl  Cl,  the  gas  (40,  10)  give  M Cl  and  H Cl, 
the  latter  equal  in  volume  to  the  chlorine  gas  taken.  In  a 
certain  sense,  this  substitution  may  be  considered  a double 
decomposition. 

5.  Finally,  quantitative  determinations  show  that  every 
equivalent  of  acetic  acid  (GO  mgr.)  has  taken  up  three  equiva- 
lents of  chlorine  gas  (3G  cc).  Hence  the  substituted  acid  is 
called  TRl-chloracetic  acid.  It  crystallizes  in  rhombohedrae, 
rather  deliquescent.  G 1.42,  F 46,  B 195.  Forms  salts 
isomorphous  with  the  corresponding  acetates. 

6.  A given  weight  of  purified  crystals  of  chloracetic  acid, 
when  saturated  by  normal  potassium  hydrate,  shows  the 
equivalent  to  be  163.5.  This  furnishes  the  simplest  demon- 
stration that  it  is  tri-chloracetic  acid.  For  the  SATURATING 
EQUIVALENT  of  acetic  acid  is  60.  Substituting  three  chlorine 
(106.5)  for  3 hydrogen  (3)  will  increase  the  weight  of  the 
equivalent  103.5,  making  it  163.5,  as  easily  confirmed  by 
experiment. 

7.  The  solution  of  potassium  chloracetate,  gently  heated 
with  an  excess  of  potassium  hydrate,  yields  CHLOROFORM 
(75,  12),  readily  recognized  by  its  odor.  This  shows  that  the 
essential  part  of  chloroform  is  a constituent  of  trichloracetic 
acid.  When  sodium  amalgan  is  added  to  the  acid  or  to  its 
salts,  the  nascent  hydrogen  produced  reduces  the  acid  to  the 
initial  state,  acetic  acid. 

8.  The  production,  by  Dumas,  of  this  remarkable  acid, 
exerted  a most  decisive  influence  on  the  development  of 
organic  chemistry  during  the  last  half  century.  The  general 
law  of  ORGANIC  SUBSTITUTION  was  now  admitted  to  be, 
EQUIVALENT  FOR  EQUIVALENT. 

9.  When  absolute  alcohol  is  saturated  at  the  freezing  point 
with  chlorine  gas,  ALDEHYDE  is  formed.  The  name  was 
coined  by  Liebig  on  the  American  OmniBUS  principle,  to  indi- 


318 


LECTURE  80. 


cate  that  the  new  substance  is  ALcohol  DEHYDrogenatus. 
The  same  product  is  obtained  by  a moderated  oxidation  of 
common  alcohol,  say  with  potassium  bichromate  and  sulphuric 
acid.  The  purified  aldehyde  is  a limpid  liquid,  of  suffocating 
odor,  G 0.80,  B 21,  soluble  in  water,  alcohol  and  ether.  It 
reduces  silver  from  ammoniated  silver  nitrate  on  gently  warm- 
ing the  solution  (mirror). 

10.  If  absolute  alcohol  is  fully  saturated  with  dry  chlorine 
gas — the  temperature  being  properly  regulated — CHLORAL  is 
formed.  It  is  purified  by  distillation,  first  from  sulphuric  acid, 
thereafter  from  quicklime.  It  is  a colorless,  oily  liquid.  G 
1.54,  F — 75  (solidifies),  B 98.  Soluble  in  water  and  alcohol. 
When  treated  with  nascent  hydrogen  (from  zinc  and  sulphuric 
acid)  it  is  reduced  to  aldehyde.  Chloral  reduces  silver  solu- 
tion like  aldehyde.  Both  form  a crystalline  precipitate  with 
sodium  bisulphite. 

11.  With  water,  chloral  combines  to  CHLORAL  HYDRATE 
which  forms  fine  colorless  crystals.  F 46,  B 97.  Hence 
chloral  is  generally  employed  as  hydrate.  It  is  a most  valu- 
able hypnotic.  When  treated  with  potassium  hydrate,  chloro- 
form is  produced.  Since  blood  is  alkaline,  chloral  probably  is 
gradually  converted  into  chloroform  in  the  system  (Liebreich)  . 
Heated  with  nitric  acid,  chloral  and  its  hydrate,  yield  tri- 
chloracetic acid,  which  is  most  readily  produced  by  this 
method. 

12.  The  reactions  given  prove  conclusively  that  alcohol, 
aldehyde,  chloral,  trichloracetic  acid  and  acetic  acid  are  VERY 
CLOSELY  RELATED  mutually  and  to  chlorform;  for  we  have 
transformed  most  of  these  bodies  into  one  or  more  of  the 
others,  and  obtained  chloroform  from  several  of  them.  To 
enter  more  fully  into  the  mechanism  of  these  changes,  we 
must  now  begin  the  study  of  their  chemical  composition. 


81.  PROXIMATE  AND  ULTIMATE 
ANALYSIS. 


1.  The  materials  furnished  by  nature  we  have  found  to  be 
essentially  COMPLEX.  The  rocks  are  all  complex,  most 
minerals  contain  admixtures  of  others — to  us,  impurities — and 
only  in  the  finest,  crystallized  specimens  do  we  find  a true 
chemical  individual,  a single  chemical  compound.  Organic 
materials  are  every  way  more  complex  than  even  the  rocks. 

2.  To  determine  the  real  CHEMICAL  COMPOUND  ACTU- 
ALLY PRESENT  in  a given  mineral  or  rock  is  often  quite 
difficult,  and  not  unfrequently  impossible.  We  can  always 
ascertain  what  elements  are  present,  but  in  many  cases  it  is 
impossible  to  state  how  they  are  combined,  or  what  proximate 
compounds  are  contained  in  the  sample.  Thus  it  is  even 
impossible  to  state  exactly  what  salts  are  contained  in  a 
given  mineral  water,  though  it  is  conventionally  done  with  a 
sublime  disregard  of  knowledge. 

3.  To  determine  the  proximate  CONSTITUENTS  OF 
ORGANIC  MATERIALS  is  not  less  difficult.  The  substances 
themselves,  being  so  readily  changed  by  even  contact  with 
neutral  solvents,  greatly  adds  to  the  difficulties.  However,  by 
care  and  skill,  the  principal  classes  of  organic  compounds  can 
be  separated.  The  methods  used  for  this  purpose  have  been 
exemplified  in  the  preceding  lectures. 

4.  Chemists  have  endeavored  to  bring  this  work  into  a 
system.  Thus  Dragendorff  has  suggested  an  order  of  pro- 
cedure for  PLANT  ANALYSIS.  Ether  removes  fats,  and  alcohol 
resins,  without  changing  starch,  gum  and  proteid  substances; 
hence  they  conveniently  precede  water  and  aqueous  solvents. 
But  no  one  system  is  applicable  in  all  cases. 

5.  A careful  review  of  the  METHODS  ACTUALLY 
EMPLOYED  in  our  preceding  lectures  will  be  more  beneficial 
than  a lengthy  exposition  of  any  special  system  of  procedure. 


320 


LECTURE  81. 


We  will  merely  add  that  these  extractions  either  have  for 
their  object  the  determination  of  the  amount  of  a certain  con- 
stituent or  the  preparation  thereof  for  further  research.  In 
the  first  case,  the  substance  used  is  limited,  and  must  be  most 
completely  exhausted  by  freely  using  reagents  and  time ; in  the 
latter  case,  both  the  material  and  the  reagents  are  used  freely, 
to  secure  the  purest  product  obtainable. 

6.  Such  methods  give  us  knowledge  of  the  proximate  con- 
stituents of  organic  substances.  They  are  methods  of  PROXI- 
MATE ANALYSIS.  Thus  we  determine  the  amount  of  nicotine 
in  tobacco,  the  percentage  of  morphine  in  opium,  of  sucrose  in 
the  cane,  of  glucose  in  the  grape,  of  starch  in  the  grain,  of 
albumen  in  the  egg.  The  results  should  not  be  stated  with  a 
precision  that  is  fictitious.  Chemists  should  not  pretend  to 
have  done  what  is  impossible.  The  thousandth  of  a per  cent, 
is  sheer  humbug. 

7.  When  an  organic  compound  has  been  produced  in  the 
pure  state,  it  may  be  subjected  to  ULTIMATE  OR  ELEMENTARY 
ANALYSIS  as  the  first  step  in  the  search  of  its  chemical  com- 
position and  structure,  expressible  by  appropriate  chemical 
formulm.  It  is  evidently  an  utter  waste  of  time  to  attempt  the 
establishment  of  a chemical  formula  for  anything  not  itself  a 
true  chemical  compound. 

8.  Lavoisier  showed  that  the  four  elements  C,  H,  N,  O 
constitute  the  bulk  of  all  organic  materials;  they  have  even 
been  termed  ORGANOGENS.  In  a very  large  number  of  com- 
pounds, nitrogen  does  not  occur;  they  consist  of  C,  H,  O only. 
On  these  facts  the  common  method  of  ULTIMATE  ANALYSIS 
BY  COMBUSTION  was  planned  by  Lavoisier,  improved  by 
Gay-Lussac,  and  practically  perfected  by  Liebig. 

9.  The  organic  compound — pure  and  dry — is  mixed  with  a 
large  excess  of  purest  copper  oxide  (Gay-Lussac),  The  mix- 
ture, heated  in  a combustion  tube,  produces  H2  O from  H, 
CO2  from  C,  and  N as  gas,  the  organic  substance  burning  at 
the  expense  of  the  oxygen  of  the  copper  oxide.  The  water 
.and  carbon  dioxide  produced  are  collected  and  weighed  as 


PROXIMATE  AND  ULTIMATE  ANALYSIS. 


321 


shown  previously  (32,  6)  ; the  volume  of  nitrogen  gas  produced 
is  measured.  The  important  PRACTICAL  DETAILS  of  such 
combustion  must  be  studied  in  the  laboratory. 

For  educational  purposes  and  elementary  LABORATORY 
PRACTICE,  small  and  short  combustion  tubes  can  be  used 
over  four  wing  gas  burners  in  a row,  the  tube  protected  with 
a sheet  of  brass  or  iron.  If  no  N,  only  the  U-tube  and  gas 
burette  with  air  lock  for  CO2  is  required;  if  N present,  insert 
potassa  bulb  and  use  gas  burette  for  N. 

10.  The  total  amount  of  CARBON  in  the  organic  substance 
taken  is  yV  of  the  increase  of  the  potassa  bulb  (CO2);  the 
amount  of  HYDROGEN  is  y of  the  increase  of  the  U-tube 
(H2  O) ; compare  31,  7 and  5.  The  weight  of  the  NITROGEN 
is  li  mgr.  per  cc  under  common  conditions  (49,  8).  The 
OXYGEN  in  the  compound  cannot  be  determined  directly 
(55,  12;  53,  12) ; it  is  determined  by  difference. 

11.  Dividing  the  weights  so  obtained  for  C,  H,  N (and  O) 
by  the  weight  of  the  substance  used,  gives  the  amount  of  each 
element  PER  UNIT  OF  WEIGHT.  Moving  the  decimal  point 
two  places  to  the  right,  gives  the  PERCENTAGE  of  each. 
This  is  all  that  quantitive  chemical  analysis  can  do.  It  is  well 
to  repeat  the  combustion  with  different  amounts  of  substance. 
The  percentage  found  should  reasonably  well  agree,  independ- 
ent of  the  absolute  amount  taken.  41,  12. 

12.  The  following  table  gives  the  analytical  results  (in  per 
•cent.)  for  a few  TYPICAL  COMPOUNDS  to  which  we  shall 


frequently  refer: 

Carbon. 

Hydrogen. 

Oxygen. 

1.  Benzol, 

. 92.3 

7.7 

.2.  Alcohol, 

. 52.2 

13.0 

34.8 

3.  Ether, 

. 64.8 

13.6 

21.6 

4.  Acetic  Ether,  .... 

. 54.4 

9.1 

36.5 

■5.  Acetic  Acid, 

. 40.0 

6.7 

53.3 

6.  Tartaric  Acid,  .... 

. 32.0 

4.0 

64.0 

7.  Sucrose, 

. 42.1 

6.4 

51.5 

S.  Urea  (N  46. 7) 

. 20.0 

6.6 

26.7 

82.  EMPIRICAL  AND  MOLECULAR 
FORMUL/E. 


1.  Several  of  the  eight  typical  organic  compounds  for 
which  the  results  of  their  elementary  analysis  are  given  in  the 
preceding  table  we  have  found  to  sustain  remarkably  CLOSE 
CHEMICAL  RELATIONS  to  one  another  (Lecture  80).  This 
applies  particularly  to  the  four  alcoholic  compounds  (Nos.  2 to 
5).  Yet  the  percentage  composition  fails  to  give  the  slightest 
indication  of  such  relationship. 

2.  But  suppose  we  express  this  per  cent,  composition  by 
the  chemical  symbols  C,  H,  O,  N.  The  value  of  these  is, 
respectively  12,  1,  16,  14  (40,  7).  That  is,  let  us  weigh  the 
carbon  by  weights  of  12  units,  oxygen  by  weights  of  16  units; 
that  is,  by  atomic  weights.  To  do  this,  we  evidently  need 
only  to  DIVIDE  THE  PERCENTAGE  BY  THE  ATOMIC  WEIGHT. 


3.  The  following  table  gives  the  results  of  this  calcula- 
tion, and  also  the  simplest  RATIOS  of  these  quotients: 


Compounds. 

c 

— Quotient. - 
H 

o 

c 

■ Ratios.  ■ 
H 

o 

1. 

Benzol, 

7.69 

7.7 

1 

1 

2. 

Alcohol, 

4.35 

13.0 

2.17 

2 

6 

1 

3. 

Ether, 

5.40 

13.6 

1.35 

4 

10 

1 

4. 

Acetic  Ether, 

5.53 

9.1 

2.28 

2 

4 

1 

5. 

Acetic  Acid, 

3.33 

6.7 

3.34 

1 

2 

1 

6. 

Tartaric  Acid, 

2.66 

4.0 

4.00 

2 

3 

3 

7. 

Sucrose, 

3.51 

6.4 

3.22 

12 

22 

11 

8. 

Urea, 

1.66 

6.6 

1.67 

1 

4 

1 

With  N 3.34 

2 

4.  The  simple  ratios  are  in  all  cases  evident,  except  for 
SUCROSE.  For  this  substance  we  see  that  the  ratio  H:0 
evidently  is  2:1.  That  of  C:0  is  nearly  36:33  or  12:11, 
which  being  tried  by  division  with  12  and  11  gives  in  both 
cases  the  quotient  0.29.  Hence  the  ratios  are  as  given.  For 


EMPIRICAL  AND  MOLECULAR  FORMUL/E. 


323 


UREA,  the  only  nitrogenous  compound  in  the  list,  the  value 
for  this  element  is  separately  stated. 

5.  These  ratios  are  all  simple  numbers;  accordingly  organic 
compounds  conform  to  DALTON’S  LAW  of  fixed,  simple 
multiple  proportions  (40,  Note).  They  represent  the  number 
of  times  each  atomic  weight  must  be  taken  to  express  the 
results  of  elementary  analysis  of  the  compound.  Thus  two 
C,  six  H and  one  O represents  exactly  the  per  cent,  of  carbon, 
hydrogen  and  oxygen  found  in  alcohol  by  elementary  analysis. 

6.  Accordingly  C2H6O  is  a chemical  formula  represent- 
ing the  quantitative  composition  of  alcohol.  In  the  same  way 
C4H10O  represents  the  results  of  the  elementary  analysis 
of  ether,  and  CH4N2O  the  composition  of  urea.  These 
chemical  formulas  are  called  EMPIRICAL  FORMULA,  be- 
cause they  express  the  mere  fact  determined  by  the  elemen- 
tary analysis  of  the  substance. 

7.  Comparing  the  four  alcoholic  compounds,  we  see  that 
these  empirical  formulas  already  mark  a CLOSE  KlNSFllP 
between  them.  They  all  have  one  oxygen  only.  Acetic 
ether  has  exactly  double  the  amount  of  both  carbon  and  hydro- 
gen found  in  acetic  acid.  In  alcohol  the  proportion  of  hydrogen 
is  increased  to  |.  In  ether  we  find  exactly  the  sum  of  alcohol 
and  acetic  ether.  All  for  equal  amounts  of  oxygen. 

8.  For  volatile  substances  it  is  easy  to  determine  their 
MOLECULAR  WEIGHT  (40,  10  to  12).  Applying  the  method 
given  to  the  volatile  substances  in  our  list,  we  find  the  follow- 
ing results:  Benzol,  78;  Alcohol,  46;  Ether,  74;  Acetic 
Ether,  88;  Acetic  Acid,  60.  Summing  up  the  atomic  weights 
of  the  empirical  formula,  we  find  it  equal  to  the  molecular 
weights  for  alcohol  and  ether;  half  the  amount  for  acetic  ether 
and  acetic  acid;  one-sixth  the  amount  for  benzol. 

9.  THE  MOLECULAR  FORMULA  OF  A COMPOUND  REP- 
RESENTS ONE  MOLECULE  OF  THE  SUBSTANCE- that  is, 
the  number  of  milligrammes  of  the  substance  which,  in  the 
gaseous  state,  occupies  as  much  space  as  two  milligrammes  of 


324 


LECTURE  82. 


hydrogen  under  the  same  temperature  and  pressure  (40,  10). 
Accordingly,  the  molecular  formulae  are:  Benzol  Ce  He,  Alco- 
hol C2  He  O,  Ether  C4  H^o  O,  Acetic  Ether  C4  Hg  O2,  Acetic 
Acid  C2  H4  O2. 

10.  The  last  three  substances  on  our  list  are  non-volatile; 
they  decompose  before  they  volatilize.  The  above  method 
accordingly  is  inapplicable.  Saturation  of  the  acid  by  normal 
alkali  would  only  give  the  equivalent,  but  not  necessarily  the 
molecule.  COMBINATION  WITH  THE  MONOVALENT  SILVER 
is  frequently  sufficient.  Thus  when  silver  acetate  is  ignited, 
it  leaves  0.645  silver  per  unit.  Since  Ag  = 108,  it  follows 
that  silver  acetate  is  166.8.  Hence  Acetate  58.8  and  H Acetate 
59.8  which  is  close  to  the  true  60.  In  this  manner  we  find 
tartaric  is  C4  He  Oe. 

11.  A method,  due  to  RAOULT,  based  upon  the  DEPRES- 
SION OF  THE  MELTING  POINT,  is  now  quite  generally  used 
for  non-volatile  substances.  It  requires  a very  sensitive  ther- 
mometer. We  cannot  here  enter  upon  the  experimental  or 
theoretical  detailSi  The  method  excellently  supplements  the 
data  needed  for  non-volatile  solids.  It  is  found  that  the 
molecular  formulas  of  sucrose  and  of  urea  are  identical  with 
their  empirical  formulae. 

12.  UREA,  CH4N2O  is  extracted  from  fresh  urine. 
Evaporate  to  one -tenth  its  volume.  Add  excess  of  strong 
nitric  acid:  Urea  nitrate  appears  in  tabular,  six-sided  crystals. 
Separate,  dissolve  (purify  by  animal  charcoal)  saturate  with 
barium  hydrate  solution  (giving  Ba  N^^®).  Evaporate  to  dry- 
ness, extract  with  alcohol,  which  dissolves  the  Urea.  Crys- 
tallize. It  forms  colorless  (white)  quadratic  prisms,  very 
soluble  in  water,  less  so  in  alcohol.  F 132.  Waste  nitro- 
genous materials  leave  the  body  in  the  form  of  urea,  about  30 
grammes  a day. 


83.  RADICAL  AND  STRUCTURAL 
FORMUL/E. 


1.  The  molecular  formulas  present  more  of  the  CHEMICAL 
RELATIONS  than  the  empirical  formulae.  Thus,  the  formula 
of  alcohol  and  acetic  acid  give  a sum  exceeding  that  of  acetic 
ether  by  H2  O;  in  fact,  this  ether  is  formed  from  the  two 
compounds  with  separation  of  water.  Again,  doubling  the 
formula  of  alcohol  gives  that  of  ether  and  of  H2  O,  agreeing 
with  the  preparation  of  common  ether.  Compare  77. 

2.  In  order  more  clearly  to  exhibit  the  chemical  relations 
or  reactions  of  the  compounds,  the  symbols  of  the  molecular 
formula  should  be  grouped  in  a manner  to  represent  the  CON- 
STITUENT RADICALS  of  the  compound.  Thus,  since  alcohol, 
C2H6O,  is  chemically  a hydrate,  it  must  contain  the 
monovalent  negative  radical  OH.  That  leaves  C2H5  which, 
accordingly,  must  represent  its  positive  radical  ethyl.  See  77,  8. 

3.  Consequently,  the  molecular  formula  C2  He  O of  alco- 
hol should  be  written  C2  H5.  OH,  to  represent  the  radicals 
or  proximate  constituents  of  the  compound,  known  to  be 
present  according  to  the  chemical  reactions  of  the  substance. 
Such  formulas  are  called  RADICAL  FORMULA. 

4.  It  is  customary  to  connect  the  formulas  of  the  radicals 
by  DOTS  OR  DASHES^-as  many  as  the  valence  of  the  same. 
Since  OH  is  monovalent,  ethyl  must  also  be  monovalent; 
accordingly  a single  dot  has  been  inserted  between  OH  and 
C2  H5.  It  will  be  readily  understood  that  the  divalent  O must 
be  marked  next  to  the  ethyl.  Compare  Lecture  40  and  43. 

5.  In  ACETIC  ACID,  C2  H4  O2,  one  hydrogen  is  replace- 
able by  monovalent  metals  (Na,  Ag)  ; hence  it  stands  as 
positive  against  the  balance  as  a negative,  C2  H3  O2.  H. 
This  shows  the  formation  of  acetic  ether  C2  H5.  O2  H3  C2 
from  alcohol  C2  H5  OH  and  acetic  acid  C2  H3  O2.H  by 


326 


LECTURE  83. 


double  decomposition  with  separation  of  water  H.  OH  or 
H Hate.  Xhe  reason  for  writing  O2  next  to  C2  H5  is  evident 
from  what  has  been  shown  above. 

6.  We  must  next  inquire  into  the  constitution  of  the  mono- 
valent electro  positive  radical  C2  H5  and  the  monovalent 
electro  negative  radical  C2  H3  O2.  The  tri-chloracetic  acid 
of  Dumas  (80,  3)  and  the  production  of  chloroform  therefrom 
(80,  7)  will  enable  us  to  unravel  the  STRUCTURE  OF  THE 
negative  RADICAL  C2  H3  O2— and  thereby  that  of  the  posi- 
tive C2  H5. 

7.  By  chlorination  of  acetic  acid  it  is  necessarily  the  H3  in 
the  radical  that  are  replaced  by  chlorine,  and  not  the  fourth, 
positive  hydrogen ; for  the  chloracetic  acid  saturates  metals 
exactly  as  does  acetic  acid  itself,  or  contains  that  same  posi- 
tive, replaceable  hydrogen  atom.  Accordingly,  TRICHLOR- 
ACETIC ACID  contains  the  monovalent  negative  radical 
C2  CI3  O2. 

8.  When  treated  with  an  alkali,  say  Ka  OH,  trichloracetic 
acid  yields  chloroform.  Analysis  shows  CHLOROFORM  to 
consist  of  carbon,  hydrogen  and  chlorine;  its  empirical  formula 
is  CH  CI3.  Its  molecular  weight  is  found  to  be  nearly  120. 
Consequently,  its  molecular  formula  is  CH  Cl 3.  Hence  the 
above  radical  must  contain  the  monovalent  radical  C CI3. 
Accordingly  it  is  C CI3.  C O2. 

9.  If  trichloracetic  acid  is  neutralized  with  sodium  hydrate 
and  the  chloroform  distilled  off,  the  residue,  after  proper  con- 
centration, will  yield  rhombic  tablets.  Identically  the  same 
crystals  are  obtained  by  saturating  the  aqueous  distillate  from 
red  ants  (Formica  rufa)  with  sodium  hydrate.  The  crystals 
accordingly  are  sodium  FORMATE. 

10.  From  these  crystals,  FORMIC  ACID  is  obtained  pure 
by  distillation  with  an  acid.  Analysis  gives  the  empirical 
formula  CH2  O2.  The  molecular  weight  is  found  to  be  46. 
It  has  but  one  H replaceable  by  Na.  Consequently,  its  radi- 


RADICAL  AND  STRUCTURAL  FORMULAE. 


327 


cal  formula  is  CH  O2.  H.  When  heated  with  concentrated 
sulphuric  acid  it  yields  carbonic  oxide  gas,  CO,  and  water 
H.  O H.  Hence  it  is  H.  CO.  OH,  for  the  radical  CARBONYL 
C O is  divalent. 


11.  The  negative  radical  C2  CI3  O2  of  trichloracetic 
acid  has  thus  been  found  to  contain  the  monovalent  C CI3 
and  CO.  O — . Its  RADICAL  STRUCTURE  is  therefore 
C CI3.CO.  O — where  the  last  dash  represents  the  monovalent 
character.  Hence  sodium  trichloracetate  is  CCl3.CO.ONa. 
Acetic  acid  accordingly  is  CH3.CO.OH,  the  last  H being 
replaceable  by  metals. 


12.  But  alcohol  C2  H5.  OH  is  convertible  into  acetic  acid 
by  oxidation.  Consequently,  the  radical  ethyl  C2H5  contains 
the  link  CH3  as  terminal;  it  is  therefore  CH3.CH2 — . 
Hence  the  STRUCTURE  OF  ALCOHOL  is  CH3.CH2.OH. 
In  this  manner  the  radical  structural  formulas  of  compounds 
are  determined  from  their  chemical  reactions.  The  results 
of  such  determinations  for  five  of  our  tabulated  compounds  are 
here  appended. 


2. 

3. 

4. 

5. 
8. 


Name.  Radical  Formulm. 

Alcohol,  . C2  Hs  OH 
Ether,  . . (C2H5)2  0 

Acetic  Ether,  C2H5.O2H3C2 
Acetic  Acid,  C2  H3  O2.  H 
Urea,  . . CO  (NH2)2 


structural  Formulm. 
CH3.  CH2.  OH 
CH3.CH2.O.CH2  CH3 
CH3.CH2.O.CO.CH3 
H.  O.  CO.CH3 
H2N.  CO.  NH2 


84.  POLYMERIC  AND  ISOMERIC 
COMPOUNDS. 

1.  At  the  close  of  the  first  quarter  of  this  century  the  outer 
walls  of  organic  chemistry  were  constructed  by  FOUR  MASTER 
BUILDERS  on  the  foundation  laid  by  Lavoisier,  Gay-Lussac 
and  Chevreul.  Faraday  in  England,  Dumas  in  France,  Liebig 
in  Germany  and  Berzelius  in  Sweden.  In  his  Annual  Reports 


328 


LECTURE  84. 


(begun  1821),  the  latter  critically  reviewed  the  work  of  the 
younger  men'. 

2.  . Liebig  had  enjoyed  the  advantages  of  the  French  school 
at  Gay-Lussac’s.  He  had  studied  the  FULMINATES  there 
(79,  12) . The  empirical  formula  of  the  terrible  explosive  silver 
fulminate  he  found  (1823)  to  be  Ag  C N O.  But  the  same 
formula  had  been  given  by  Wohler  for  the  non-explosive  silver 
CYANATE,  a year  previously.  Liebig,  thinking  that  possibly  an 


WOHLER. 

error  had  been  committed,  repeated  all  analyses,  but  again 
obtained  the  same  results.  Hence  two  entirely  different  bodies 
are  represented  by  the  same  empirical  formula! 

3.  A few  years  later  (1828),  Wohler,  working  on  potas- 
sium cyanate,  Ka  O Cy,  found  that  by  heating  a mixture  of 
equivalent  solutions  of  this  salt  and  of  ammonium  sulphate, 
Am2  O4  S,  the  dry  residue,  upon  extraction  with  alcohol,  gave 
CRYSTALS  OF  UREA.  (72, 12) . Double  decomposition  yielded 


POLYMERIC  AND  ISOMERIC  COMPOUNDS. 


329 


difficultly  soluble  Ka  the  other  compound,  Am  O Cy 

had  evidently  changed  into  Urea. 

4.  Writing  out  the  radicals  Am  and  Cy,  the  ammonium 
cyanate  is  represented  by  the  formula  NH4  O.  CN,  while  urea 
(83,  12)  is  represented  by  H2N.  OC.  NH2.  Evidently,  the 
hydrogen  has  changed  place,  and  carbon  and  oxygen  have 
combined  more  intimately,  nitrogen  and  carbon  less  so,  the 
nitrogen  now  being  partly  saturated  by  the  additional  hydrogen. 
This  has  been  called  a synthesis  of  urea;  but  it  is  simply  an 
“atom  WANDERUNG.” 

5.  About  the  same  time  (1825)  Faraday  discovered  the 
liquid  hydrocarbon  BENZOL  (62,  6)  in  coal  tar.  On  analysis 
he  found  C H as  the  empirical  formula.  He  was  amazed  at 
this  result,  because  the  same  formula  was  considered  to  rep- 
resent the  gas  called  olefiant  gas,  obtained  by  gently  heating 
the  mixture  of  one  volume  of  alcohol  and  six  volumes  of  con- 
centrated sulphuric  acid. 

6.  Berzelius  for  several  years  supposed  these  results  to  be 
erroneous.  But  while  investigating  TARTARIC  ACID  and  tar- 
trates (1831),  he  discovered  that  RACEMIC  ACID  had  exactly 
the  same  quantative  composition  as  tartaric  acid,  the  analyses 
of  both  leading  to  exactly  the  same  empirical  formula.  Now  he 
admitted  the  facts  stated  and  coined  the  names  still  in  use: 
polymeric  and  isomeric  compounds. 

7.  In  the  terms  of  the  present,  different  substances,  having 
the  same  percent  composition,  and  therefore  expressed  by  the 
same  empirical  formula,  are  either  POLYMERIC  or  ISOMERIC, 
according  as  their  molecular  formula  is  different  or  identic. 
In  the  latter  case,  the  radical  formulae  differ. 

8.  The  empirical  formula  of  olefiant  gas  now  is  known  to 
differ  from  that  of  benzol;  it  is  CH2  and  not  CH.  But 
ACETYLENE  (which  Berthelot  obtained  by  direct  synthesis, 
forty  years  ago,  and  which  now  is  produced  in  quantity  by 
Moissan  from  his  calcium  carbide  and  water)  has  identically 
the  same  percentage  composition  as  benzol,  and  therefore  the 
same  empirical  formula  CH. 


330 


LECTURE  84. 


9.  The  molecular  weight  of  benzol  is  78  (82,  8),  but  that 
of  acetylene  is  found  to  be  26  only.  Accordingly,  while  the 
molecular  formula  of  benzol  is  CeHe  (82,  9),  acetylene  is  rep- 
resented by  the  molecular  formula  C2H2.  — It  thus  appears 
that  a benzol  molecule  weighs  three  times  as  much  as  a mole- 
cule of  acetylene.  Berthelot  has  indeed,  CONDENSED 
ACETYLENE  TO  BENZOL  by  passing  it  through  a red  hot 
tube.  He  has  also  decomposed  benzol  into  acetylene. 

10.  The  empirical  formula  Ag  C N O represents  both  silver 
cyanate  Ag.  O.  CN  and  silver  fulminate  AggrCib  where  a 
stands  for  O2N  and  bforCN.  These  compounds  are  isomeric. 
The  radical  formulae  for  ammonium  cyanate  and  for  urea  have 
been  given  in  4;  these  compounds  are  isomerics,  represented 
by  their  common  empirical  formula  CH4  N2  O.  The  case  of 
tartaric  and  racemic  acids  is  of  a higher  order,  and  will  be  con- 
sidered in  the  next  lecture. 

11.  Since  the  masters  brought  the  nature  of  isomerism  and 
and  polymerism  to  light,  these  phenomena  have  been  found  to 
be  common  among  organic  compounds.  Thus  the  molecular 
formula  of  ETHER,  C4H10O  represents  quite  a number  of 
different  isomerics.  Among  the  most  common  of  these  is 
BUTYL  ALCOHOL,  C4H9.OH  or  CH3 .CH2 .CH2.CH2 .OH. 
It  is  a liquid  (obtainable  from  butyric  acid)  of  pleasant  odor, 
requiring  12  volumes  of  water  for  solution.  G 0.81  (at  20), 
B 117.  Nobody  could  possibly  confound  such  a liquid  with 
ether;  yet  it  has  not  only  the  same  empirical,  but  even  the 
same  molecular  formula. 

12.  In  view  of  these  facts,  it  is  manifest,  that  the  empirical, 
and  even  the  molecular  formula  of  compounds,  are  of  com- 
paratively little  value.;  they  really  give  no  insight  into  the 
chemical  nature  of  the  same,  for  they  each  one  apply  to  many 
entirely  different  isomeric  or  polymeric  compounds  that  often 
could  not  be  confounded  by  the  merest  tyro.  THE  CHEMICAL 
NATURE  OF  COMPOUNDS  IS  EXPRESSED  IN  THEIR  RADICAL 
AND  STRUCTURAL  FORMULA. 


85.  RIGHT-  AND  LEFT-HANDED 
COMPOUNDS. 


1.  Further  study  of  isomerics  has  revealed  the  existence 
of  compounds  containing  exactly  the  same  chemical  radicals 
and  yet  so  different,  one  from  the  other,  that  not  only  man, 
but  even  monads  readily  can  distinguish  them.  The  case  of 
tartaric  and  racemic  acid  of  Berzelius  is  the  first  instance  of 
this  kind.  84,  6. 

2.  Recent  researches  have  shown  that  these  compounds 
differ  one  from  the  other  as  does  the  glove  of  the  right-hand 
from  that  of  the  left.  Though  both  hands  are  identical  in 
most  respects,  they  are  not  equal,  but  symmetric — the  one  is 
exactly  like  the  reflected  image  of  the  other.  Chemical  com- 
pounds of  this  kind  are  designated  as  LEFT-  (1)  and  RIGHT 
(d,  dextro)  -HANDED  modifications  or  geometrical  isomerics. 

3.  These  differences  are  by  no  means  hard  to  recognize. 
When  crystallized,  the  substances  show  it  to  the  unaided  eye. 
When  in  solution,  they  show  it  so  plainly  in  POLARIZED 
LIGHT  that  one  of  the  most  common  methods  of  analysis  of 
organic  compounds  is  based  upon  this  difference  (45,  6). 
Common  officers  of  the  civil  government  determine  import 
duty  and  credit  bonus  on  sugar  by  this  method  of  polarization. 
Even  monads  will  eat  the  one  and  refuse  the  other  of  these 
isomerics. 

4.  THE  HISTORY  of  this  line  of  research  is  both  fascinat- 
ing and  instructive.  If  we  could  give  a lecture  course  on  this 
subject  instead  of  a single  lecture,  we  would  have  ample 
material  to  sustain  the  interest  ’till  the  close.  The  researches 
leading  to  these  wonderful  results  also  sharply  mark  the 
difference  between  routine  work  of  detail  and  the  discoveries 
due  to  genius.  The  masses  never  can  do  the  work  of  the 
master. 


332 


LECTURE  85. 


5.  The  now  popular  method  of  SPECIAL  RESEARCH  im- 
ported, duty  free,  with  cheap  parchments,  is  as  impotent  as 
the  empty  formula  of  Bacon  and  the  hairsplitting  verbiage  of 
the  scholast.  On  the  contrary,  we  see  the  work  of  physicist 
(Biot)  astronomer  (Arago,  Sir  John  Herschel)  crystallographer 
(Hauy,  Mitscherlich)  and  chemist  (Berzelius,  Pasteur)  con- 
centrated in  the  one  final  result  under  consideration. 

6.  To  approach  this  subject  understandingly,  we  must,  for 
the  moment,  leave  our  ethers  and  acids  with  the  chemists  and 
examine  once  again  the  quartz  crystal  with  the  physicist  and 
crystallographer.  ARAGO  had  discovered  (1811)  that  it  turns 
the  plane  of  polarized  light,  passing  parallel  to  its  axis.  BlOT 
had  found  that  this  rotation  is  exactly  proportional  to  the 
thickness  of  the  plate,  and  that  many  organic  compounds 
(sugars,  volatile  oils,  alkaloids)  possess  the  same  property. 

7.  The  most  important  forms  of  the  crystals  of  quartz  are 
represented  on  the  upper  part  of  p.  65.  The  dominant  prism 
r and  rhombohedr^e  P and  z have  been  described  (10,  6). 
Close  inspection  had  already  shown  HAUY  the  rhombic  facets  s 
and  the  (plagihedral)  trapez  facets  x in  the  zone- like  belt  P s 
X r (fig.  5) . The  angles  are  Ps  151.1,  r x 168.0  and  s r 142.0. 
The  rhombic  facets  generally  show  a high  luster,  and  may  be 
striated  parallel  to  edge  Pr  (figs.  6,  7).  The  facets  x are 
usually  dim. 

8.  The  astronomer  SIR  JOHN  HERSCHEL,  in  1820,  dis- 
covered that  in  right-handed  quartz  (upper  P s x r to  right, 
fig.  7)  the  polarized  ray  of  light  is  turned  to  the  right,  while 
in  left-handed  quartz  (P  s x r to  left,  fig.  6)  the  light  is  turned 
in  the  opposite  direction.  We  now  use  plates  of  such  crystals 
in  finer  polarizing  microscopes.  The  order  of  succession  of  the 
colors  on  turning  the  analyzer  indicates  the  nature  of  the 
crystal,  whether  right-  or  left-handed. 

9.  Solutions  of  tartaric  acid  show  polarization  while  solu- 
tions of  the  isomeric  racemic  acid  show  none.  But  PASTEUR 
(1848)  found  that  ammonium-sodium  racemate  gave  on 


RIGHT-  AND  LEFT-HANDED  COMPOUNDS. 


333 


crystallization,  crystals  showing  similar  plagihedral  facets, 
either  to  the  right  or  to  the  left  of  certain  main  forms,  precisely 
as  we  find  it  in  quartz.  Picking  these  crystals  by  hand, 
separating  the  acids  by  Scheele’s  method  (63.2)  and  dissolv- 
ing these  separately,  he  obtained  from  the  non -active  racemic 
acid  both  a right-handed  and  a left-handed  acid.  The  first  is 
identical  with  tartaric  acid. 

10.  Accordingly,  RACEMIC  ACID  is  merely  a combination 
of  r (old)  and  1 (new)  tartaric  acid.  Pasteur  demonstrated 
this  conclusion  by  synthesis,  which  took  place  with  notable 
evolution  of  heat.  The  compound  resulting  was  racemic  acid. 
The  molecular  formula  of  tartaric  acid  C4H6O6  indicates  none 
of  these  relations.  It  is  dibasic,  containing  twice  CO. OH. 
Radically  it  is  HO.CO.CHX.CHX.CO.OH  where  X stands 
for  hydroxyl  OH.  Non -active  isomerics  are  marked  i 
(inactive).  Doubled  (neutral),  meso. 

11.  Now  all  the  formulas  of  organic  compounds  given  show 
plainly  that  carbon  may  be  considered  quadrivalent;  compare 
also  40,  4,  5.  Remembering  this,  the  formula  just  quoted 
shows  tartaric  acid  to  contain  two  carbon  atoms  each  combined 
mutually  and  with  the  monovalent  H,  OH  marked  X and 
CO. OH,  the  weights  of  which  are  1,  17,45.  The  fourth 
valence  holds  exactly  half  the  entire  compound,  or  75. 

12.  In  other  words,  each  one  of  the  central  carbons  is  com- 

bined or  loaded  with  the  weights  1,  17,  45,  75,  all  four  unequal. 
The  load  is  entirely  unsymmetric.  A carbon  atom  so  combined 
is  called  ASYMMETRIC  by  VAN’T  HOFF  (Holland,  1874)  and 
LE  BEL  (France,  1874),  who  independently  generalized  this 
condition:  No  rotary  polarization  without  at  least  one 

asymmetric  carbon  atom. 


Pasteur  before  Biot.  The  research  here  reported  was  the  first  one 
made  by  Pasteur,  submitted  to  the  Academy  of  Sciences  of  Paris. 
The  old  investigator  of  rotary  polarization,  Biot,  was  to  report  on  the 
merit  of  the  work  of  young  Pasteur.  The  following  is  a synopsis  of  the 


334 


LECTURE  85. 


account  of  the  examination  made  by  Biot,  as  reported  by  Pasteur  him- 
self in  his  Lecture  on  January  2oth^  1860,  before  the  Chemical  Society 
of  Paris: 

Biot  requested  me  to  call  or.  him  and  to  repeat  my  experiments  in 
his  presence.  He  gave  me  racemic  acid^  which  he  had  himself  optically 
examined,  and  found  to  be  entirely  inactive.  I converted  this  in  his 
presence,  into  the  Ammonio-Sodium  salt,  using  the  ammonia  and  soda 
furnished  by  himself  (Biot).  The  solution  was  set  aside  in  his  labora- 
tory tor  spontaneous  evaporation.  When  30  to  40  grammes  of  crystals 
had  separated,  he  again  requested  me  to  call  at  the  College  de  France, 
in  order  to  pick  out,  under  his  very  eye,  the  right-  and  left-handed 
crystals.  He  asked  me  to  repeat  the  declaration,  that  the  crystals  which 
I should  place  to  his  right  would,  in  solution,  turn  the  polarized  light  to 
the  right,  and  those  which  I should  place  to  his  left  would  deflect  the  ray 
to  the  left.  After  I had  done  the  work  accordingly,  he  said  that  he 
would  himself  do  the  rest.  He  carefully  prepared  the  solutions  from 
weighed  quantities,  and  when  he  was  ready  to  make  the  flnal  observation 
by  means  of  the  polarizing  apparatus,  he  called  me  again  into  his  room. 
He  first  put  the  most  important  solution  into  the  apparatus,  namely  the 
solution  which  was  to  deflect  to  the  left.  Without  taking  a reading,  at 
the  mere  aspect  of  the  tints  of  color  in  the  two-halves  of  the  field  (of 
the  Soleil  Saccharimeter)  he  instantly  recognized  the  presence  of  a 
deflection  to  the  left.  The  gray-haired  man  was  profoundly  moved;  he 
grasped  my  hand  and  said : Wy  dear  boy,  I have  loved  science  all  my 
life  so  much  that  I hear  my  heart  beat  for  joy  at  this  sight.” 

We  may,  with  Pasteur,  call  attention  to  the  fact  that  Biot  had,  for 
twenty  years,  urged  chemists  to  study  rotary  polarization  as  a means  of 
investigating  the  structure  of  chemical  compounds.  Pasteur  was  the 
first  who  did  so  and  was  richly  rewarded.  Strange  as  it  may  seem,  this 
very  research  led  him  directly  to  his  wonderful  biological  discoveries 
which  now  dominate  medicine  (71.  ii).  For  searching  for  methods  of 
separation  of  these  right-  and  left-handed  substances,  which  deport 
themselves  alike  to  all  chemical  reagents,  he  naturally  tried  the  action 
of  ferments.  Now  tartrates  were  known  to  ferment  readily.  Accord- 
ingly he  added  this  ferment  to  a solution  of  ammonium  racemate,  to 
which  the  necessary  albumin  had  been  added  as  ferment-food  (71.  4). 
The  liquid  was  placed  in  the  tube  of  his  polarizing  apparatus.  Race- 
mate  being  inactive,  no  deflection  was  seen  at  the  beginning.  But  as  the 
fermentation  spread,  the  plane  of  polarized  light  turned  towards  the  left. 
The  ferments  (from  right-handed  tartrates)  consumed  this  right-handed 
tartrate  of  the  ammonium  racemate.  The  left-handed  portion  was  not 
attacked — and  caused  the  turning  of  the  plane  of  polarized  light. 

The  ox  eats  no  flesh  and  the  lion  refuses  to  eat  grass.  To  the  ferment 
cells  of  right-handed  tartrates,  the  left-handed  isomeric  evidently 
appears  as  different  as  do  flesh  and  grass  to  the  higher  animals. 


86.  TETRAHEDRON  AND  BENZOL  RING. 


1.  Modern  scientists  frequently  deride  the  views  of  the 
philosophers  of  Ancient  Greece  on  the  co,nstitution  of  things. 
The  use  of  the  regular  polyhedrae  by  Plato  (Tim^os)  is  a 
favorite  topic  of  this  kind.  Nevertheless,  the  chemical  litera- 
ture of  to-day  places  PLATO’S  TETRAHEDRON  at  the  head  of 
the  science.  It  has  become  the  nucleus  of  all  organic  com- 
pounds. It  is  CH4. 

2.  When  Van’t  Hoff  and  Le  Bel  had  recognized  the  asym- 
metric carbon,  they  both  concluded  that  the  four  hydrogen 
atoms  of  CH4  occupy  the  corners  and  the  carbon  atoms  the 
center  of  a regular  tetrahedron.  In  series;  these  TETRA- 
HEDRAE  WERE  STRUNG  along  a line,  corner  to  corner,  inde- 
pendent of  the  fundamental  laws  of  mechanics. 

3.  THE  PUZZLE  of  placing  three  hundred  soldiers  on  the 
ramparts  of  a square  fort  so  that  each  side  shall  be  defended 
by  one  hundred  men  is  commonly  solved  by  placing  fifty  in  the 
middle  of  each  side  and  twenty-five  at  each  corner.  Such 
solutions  answer  the  purpose  of  a puzzle  admirable  till  the 
enemy  attacks  all  sides  at  once.  As  reward  for  this  puzzle - 
solution,  Van’t  Hoff  was  called  from  Holland  to  the  chair  of 
chemistry  in  the  University  of  Berlin,  Germany. 

4.  It  is  only  after  almost  fifteen  years  that  the  mechanical 
absurdity  of  this  stringing  of  tetrahedrae  was  recognized.  The 
utter  absence  of  scientific  understanding  in  the  highest  circles 
of  German  chemistry  is  strikingly  evidenced  by  the  report  in 
Bischoff’s  Big  Book  (1894)  on  Stereochemistry;  1060  pages 
only.  He  simply  prints  (p.  79)  both  pictures;  the  one  marked 
“jetzt”  and  the  other  marked  “fruher.”  No  comments. 
“ALLES  WURST.” 

5.  If  the  “latter  view”  of  Van’t  Hoff  is  taken,  the  alcoholic 
compounds  necessarily  have  a CORKSCREW  STRUCTURE. 
This  structure  of  alcoholic  compounds  would  seem  to  be  emi- 


336 


LECTURE  86. 


nently  appropriate  to  those  who  know  alcohols  numbers  two 
and  five  only.  Really,  the  theory  demands  no  serious  consider- 
ation here.  See  my  paper,  Comptes  Rendus,  T.  113,  p.  745; 
1891. 

6.  Ostwald  (1896)  in  his  History  of  Electro-Chemistry 
(only  1,152  pages,  mostly  reprints)  repeatedly  castigates 
German  scientists  of  a preceding  period  for  succombing  to  the 
disease  “ Naturphilosophie.”  In  a near  future,  the  chemists 
of  the  present  age  will  probably  be  said  to  have  succombed  to 
the  TETRAHEDRAL  BACILLUS. 

7.  There  is  another,  and  considerably  older  picture  in  mod- 
ern chemical  literature.  It  is  the  HEXAGON,  introduced  by 
Kekule  (1866)  to  represent  the  constitution  of  BENZOL, 
CeHe.  The  six  carbons  are  supposed  to  form  a hexagon  and 
to  be  tied  alternately  singly  and  doubly,  and  outwardly  com- 
bined with  one  hydrogen  each.  Thus  the  four  valencies  of 
each  carbon  are  supposed  to  be  saturated.  See  diagram. 

8.  This  view  has  rendered  undoubted  services  to  the 
progress  of  chemical  science.  It  has  been  frequently  attacked, 
also  on  thermochemical  grounds  by  Thomsen,  of  Copenhagen. 
Prismatic  and  other  more  elaborate  formulae,  have  been  pre- 
sented as  substitutes.  The  solution  of  Kekule  appears  to 
represent  all  facts  known.  That  IT  IS  IN  ACCORDANCE 
WITH  MOLECELAR  MECHANICS  we  have  shown  in  our 
Principles  of  Chemistry,  1874,  and  in  the  Comptes  Rendus, 
1875. 

9.  The  relations  between  BENZOL  AND  ACETYLENE, 
discovered  by  Berthelot  (84,  9)  are  strong  facts  in  favor  of 
this  ring-form.  The  formula  resolves  itself  in  the  same  three 
parts,  held  by  a double  tie.  Each  of  these  parts  represents 
one  of  acetylene.  This  indicates  also  that  the  carbon  atoms 
really  do  not  form  a regular  hexagon,  but  correspond  in  position 
to  the  rhombohedron. 

10.  NAPHTALENE  (74,  2)  is  a condensed  form  of  benzol; 
two  atoms  united  under  loss  of  two  carbons.  The  accepted 


ISi  O O Q -To  I 

-ail.  f T ^ 

oA^o 

20iCu.S^°iKo.puMK. 

fr/u,. 

& JStI}' 

* 

‘ SoJ^ 

S.L  iK-.h,  5 

:y-k^ 


22'-^^ 


2,r2 


(^. 


I <57i  0^0* 

/ O*  . I . o 

Ci  fcri'c  Aci^.^* 


SoL.clcjW, 


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Bl-ACKBOAftD  SIA&aAMS 


y'  ■ 


-y?.. 


TETRAHEDRON  AND  BENZOL  RING. 


337 


•constitution  is  shown  in  the  diagram  given.  The  two  carbons 
common  to  the  two  benzol  rings  are  tied  doubly;  hence  only 
four  carbons  in  each  ring  can  unite  with  hydrogen.  The 
formula  for  naphtalene  must  be  CioHg. 

11.  The  trivalent  nitrogen  may  take  the  place  of  one  carbon 
in  either  benzol  or  naphtalene.  Being  trivalent  it  cannot  com- 
bine with  an  outer  hydrogen,  so  that  these  compounds  contain 
respectively  5 and  7 hydrogen  only.  C5  N H5  is  called  PYRI- 
DINE (74,  10)  and  C9  N H7  is  CHINOLINE  (74,  11).  See 
diagrams  given. 

12.  Many  higher  condensations  exist.  Thus  ANTHRA- 
CENE (74,  3)  is  considered  to  result  from  two  complete  ben- 
zol rings  tied  rather  curiously  by  2 CH  as  shown  in  the  dia- 
gram. The  structure  looks  like  three  benzol  rings,  the  middle 
of  which  has  a diagonal  tie.  Formula  C14  Hio-  These  forms 
are  the  only  ones  that  require  attention. 


87.  ALCOHOLIC  COMPOUNDS. 

1.  The  general  chemical  principles  exposed  in  the  preced- 
ing lectures  were  obtained  in  the  study  of  the  compounds 
■extracted  from  the  most  common  organic  prime  materials.  We 
will  now  take  a look  at  the  principal  CLASSES  OF  COM- 
POUNDS. A detailed  systematic  exposition  of  organic  com- 
pounds must  be  looked  up  in  any  of  the  numerous  manuals. 

2.  All  organic  compounds  may  be  roughly  arranged  in 
THREE  GREAT  DIVISIONS.  Aromatic  compounds  contain 
the  benzol  ring.  Alcoholic  compounds  do  not  contain  such  a 
ring.  Complex  compounds  may  contain  both  alcoholic  and 
aromatic  radicals. 

3.  Of  true  alcoholic  compounds,  the  acids  have  always 
been  most  prominent.  Scheele  and  Chevreul  opened  the  way 
in  this  investigation.  We  have  seen  that  all  these  acids  con- 


338 


LECTURE  87. 


tain  the  radical  carboxyl  CO  united  to  hydroxyl  OH.  That 
is,  acids  contain  the  TERMINAL  — CO.  OH  or  summarily 
CO  H.  The  dash  indicates  that  this  terminal  is  mono- 
valent. 

4.  In  formic,  acetic,  butyric,  palmitic  and  stearic  acids  we 
find  this  acid-terminal  only  once;  these  acids  are  called  mono- 
basic. In  oxalic  and  tartaric  acids,  this  terminal  occurs  twice; 
they  are  said  to  be  dibasic.  In  tribasic  citric  acid  this  termi- 
nal occurs  three  times.  These  are  about  the  only  alcoholic 
acids  specially  studied  in  the  preceding.  The  NUMBER  of 
times  this  terminal  occurs  in  any  acid  determines  the  SATU- 
RATING CAPACITY  of  that  acid. 

5.  If  we  determine  the  formulas  of  the  radicals  united  with 
this  terminal  in  the  first  five  acids  enumerated,  we  find  them 
to  be  H,  CHg,  C3H7,  Ci5  H3,,  C17  H35.  For  any  number 
m of  carbon  atoms,  these  monovalent  alcohol  radicals  are  seen 
to  contain  twice  that  number  of  hydrogen  atoms  and  one  over 
(2  m + 1).  The  ALCOHOLIC  RADICAL  Rm  is  therefore 
expressed  by  the  general  formula  Cm  H^m+i. 

6.  Oxalic  acid  is  that  terminal  united  with  itself  or 
HO. CO— CO. OH.  The  formula  of  tartaric  acid  has  already 
been  given  (85,  10).  CITRIC  ACID  (63,  5)  contains  the  acid 
terminal  — CO.  OH  three  times,  being  united  to  each  carbon 
of  the  trivalent  alcohol  radical  CH2.  CH.  CH2.  Formulae  of 
this  kind  become  rather  complex  when  written  out  in  full,  and 
are  especially  difficult  for  the  printer.  Hence  we  only  have 
given  the  radicals,  separately. 

7.  It  is  much  preferable  to  REPRESENT  COMPLEX 
FORMULAE  GRAPHICALLY.  To  avoid  too  great  speciali- 
zation we  represent  the  atoms  by  circles  or  disks.  The  tetra- 
valent  carbon  by  a large,  black,  the  divalent  oxygen  by  a 
smaller  open  circle,  and  the  monovalent  hydrogen  by  a dot. 
The  trivalent  nitrogen  we  represent  by  a triangle.  If  ties 
are  to  be  marked,  they  may  be  represented  by  straight  lines 
as  usual. 


ALCOHOLIC  COMPOUNDS. 


3:i9 


8.  THE  DIAGRAM  and  fully  written  out  formula  of  citric 
acid  will  once  for  all  show  the  advantages  of  this  representa- 
tion of  organic  compounds  (see  plate).  We  wish  to  insist 
that  these  diagrams  are  merely  to  be  taken  as  graphic  formulas 
which  it  is  much  easier  to  write  and  to  read  than  the  complex, 
fully  written  out  DEVELOPED  FORMULA  of  the  books  that 
are  the  despair  of  the  compositor  and  the  student. 

9.  By  strong  reducing  agents — such  as  nascent  hydrogen 
produced  by  sodium  amalgam  in  the  open,  or  hydriotic  acid  in 
the  autoclave— THE  ACIDS  CAN  GENERALLY  BE  REDUCED 
TO  AN  ALCOHOL.  In  that  case,  the  carbonyl  CO  is  reduced 
to  CH2.  Thus  acetic  acid  CH3.CO.OH  yields  common 
(ethyl)  alcohol  CHg.  CH2.  OH.  This  process  is  quite  general 
and  reversible.  Alcohols,  by  oxydizing  agents,  are  converted 
into  acids  (77,  1). 

10.  ETHERS  ARE  EITHER  OXIDES  OR  SALTS.  The  first 
may  be  compared  to  water  H2  O or  H.O.H  in  which  the 
hydrogen  is  supposed  to  be  replaced  by  two  monovalent 
alcohol  radicals.  These  are  the  same  in  simple,  different  in 
mixed  ethers.  Examples  Et.  O.  Et  and  Et.  O.  Me,  where  Me 
represents  methyl  CH3.  The  ether  salts  contain  an  acid 
radical  and  an  alcohol  radical.  Example,  acetic  ether,  Et.  O.  Ac 
where  Ac  stands  for  acetyl.  CH3.CO — . 

11.  AMINES  AND  AMIDES  may  be  compared  to  ammonia 
NH3  exactly  as  ethers  to  water.  In  amines,  the  hydrogen  of 
ammonia  may  be  supposed  to  have  been  replaced  by  alcohol 
radicals;  in  the  amides  we  have  one  or  more  acid  radicals.. 
Thus  ethyl  amine  Et  N H2  and  acetyl  amide  Ac  N H2  (Ace- 
tamide). The  latter  is  a crystalline  solid,  F 75,  B 222;  the 
former  is  a very  limpid,  ammoniacal  liquid,  G 0.7,  B.  18.4. 
Urea  is  simply  CARBAMIDE  (82,  12).  A.  W.  Hofman  (p.  34) 
worked  this  field  very  successfully  and  gave  German  chemistry 
that  industrial  character  it  has  since  retained. 

12.  ALDEHYDES  (80,  9)  are  intermediate  between  acid 
and  alcohol;  they  contain  the  monovalent  terminal  — COH. 


340 


LECTURE  88. 


Ketones  contain  carbonyl  united  with  two  alcohol  radicals 
R,  R';  they  may  be  considered  as  ethers  in  which  the  oxygen 
has  been  replaced  by  carbonyl.  Their  general  expression  is, 
accordingly,  R-CO  — R'.  If  R = R'  = Me  = CHg  we  have 
acetone,  CHg.  CO.  CHg.  75,  12. 


88.  AROMATIC  COMPOUNDS. 

1.  The  aromatic  compounds  more  READILY  UNDERGO 
SUBSTITUTIONS  than  the  alcoholic  compounds.  The  benzol 
ring  is  wonderfully  ready  to  exchange  its  hydrogen.  Further- 
more, the  grouping  of  the  carbons  in  the  ring  gives  rise  to  an 
almost  infinite  number  of  isomerics. 

2.  Treating  benzol  (62,  6;  74,  1)  with  the  mixture  of  con- 
centrated nitric  and  sulphuric  acid  (79,  8).  we  do  not  obtain  a 
saponifiable  nitrate,  but  NITRO-BENZOL.  Investigation  has 
shown  that  benzol  exchanges  one  hydrogen  for  the  monovalent 
radical  nitryl,  NO2.  At  the  same  time,  the  hydrogen  is 
oxidized  to  water.  Ce  Hg  thus  changes  to  Cg  H5.  NO2.  The 
monovalent  radical  C5  H5  is  called  phenyl;  for  it  exists  in 
phenol.  It  may  be  represented  by  Ph. 

3.  NlTRO-BENZOL,  Ph.  NO2  is  a yellowish  liquid,  of  the 
odor  of  oil  of  bitter  almonds,  for  which  it  is  substituted  in 
cheap  perfumes.  G 1.3,  F 3 (solidifies)  B 220.  Acted  upon 
by  nascent  hydrogen  (from  iron  and  acetic  acid)  it  is  reduced 
to  ANILINE,  Ph.  NH2  (74,  12),  which  really  is  prepared  in 
this  manner  from  benzol  for  the  manufacture  of  aniline  colors. 

4.  Crushed  bitter  almonds  ferment  upon  the  addition  of 
water,  and  yield  a distillate  which  gives  a crystalline  precipi- 
tate with  sodium  bisulphite.  Accordingly,  it  contains  an 
aldehyde  (80,  10)  which  is  separated  from  the  crystals  by 
means  of  sodium  hydrate,  and  purified  by  rectification  from 
calcium  chloride.  It  is  called  BENZALDEHYDE  and  is  found 
(Woehler,  1832)  to  be  Ph.  COH  (compare  87,  12). 


AROMATIC  COMPOUNDS. 


341 


5.  BENZALDEHYDE,  Ph.  COH,  is  a colorless,  highly 
refractive  liquid,  of  a pleasant,  characteristic  odor  and  an 
aromatic  taste.  1.07  at  0,  B 179.5.  By  moderate  heat  it 
gives  benzol  Ph  H and  carbonyl  CO  gas.  Exposed  to  the 
air  and  sun  light,  this  aldehyde  changes  to  its  acid  (87,  12), 
namely  benzoic  acid,  Ph.CO.OH,  which  see  (62,  7). 

6.  PHENOL  (74,  6)  upon  analysis  is  found  to  be  Ph.  OH 
or  phenyl  hydroxyl.  It  can  be  obtained,  by  a somewhat 
circuitous  way,  from  benzol.  By  dropping  melted  phenol  into 
boiling  nitric  acid,  tri-nitro  phenol  C6H2(N02)3  OH  is 
obtained,  commonly  called  carbazotic  or  PICRIC  ACID.  It 
forms  yellow  lamellar  crystals,  difficultly  soluble  in  water. 
On  sudden  heating  it  explodes.  Its  salts  are  very  explosive. 
It  dyes  yellow  a thousand  times  its  own  weight  of  silk. 

7.  This  and  other  nitro-phenols,  when  reduced,  give 
amido-phenols.  The  ethyl  ethers  hereof  are  called  phene- 
tidins.  One  of  these  treated  with  glacial  acetic  acid  yields 
the  modern  synthetic  remedy  PHENACETIN,  forming  shining 
crystals,  without  odor  and  almost  without  taste;  F 135. 
It  is  an  antipyretic.  Chemically  it  is  acet-para-phenetidin, 
C6H4  A B,  where  A stands  for  — O.C2H5  and  B for 
— NH(C2H30). 

8.  After  much  research  it  has  been  ascertained  that  phenol 
with  one  nitryl  gives  three  distinct  isomerics,  called  ORTHO-, 
META-  and  PARA-NITRO-PHENOL,  or  designated  more 
briefly  by  the  initmls  o,  m and  p.  It  has  further  been  ascer- 
tained, that  counting  from  the  carbon  combined  with  hydroxyl 
in  phenol,  ortho  compounds  have  the  second,  meta  the  third 
and  para  the  fourth  carbon  combined  with  nitryl.  See  diagram. 

9.  Each  of  the  other  aromatic  hydrocarbons  gives  series  of 
compounds  corresponding  to  the  benzol  compounds  here 
barely  hinted  at.  Furthermore,  the  number  of  isomerics  rapidly 
increases  with  the  complexity  of  the  hydrocarbon.  Thus 
naphtalene  (74,  2)  gives,  when  one  hydrogen  is  replaced  by 
hydroxyl,  the  two  NAPHTOLS  (74,  8)  which  are  isomeric; 
both  expressed  by  the  same  formula  C10H7.OH. 


342 


LECTURE  89. 


10.  If  a hydrogen  atom  next  to  one  of  the  two  carbon 
atoms,  common  to  the  two  benzol  rings,  has  been  replaced, 
it  is  the  a-naphtol.  If  the  outer  hydrogen  atom  has  been 
replaced,  the  ,i3-naphtol  results.  How  chemists  have  finally 
determined  these  questions  of  PLACE  IN  THE  ATOM  is  a 
matter  entirely  for  special  study  and  altogether  beyond  the 
scope  of  this  introduction.  How  these  results  are  confirmed 
and  established  by  mechanical  laws  will  be  indicated  in  the 
last  ten  lectures  of  this  course. 

11.  Still  more  numerous  are  the  isomerics  obtained  by 
substitution  in  pyridine  and  chinoline  (86,  11  and  74,  10,  11). 
Ladenburg  succeeded  (1888)  in  combining  normal-propyl, 
CH3.CH2.CH2 — in  the  a-position  (i.  e.  next  to  the  nitrogen) 
in  piperidine  (74,  10)  ; the  product  was  identical  in  all  chemi- 
cal reactions  and  in  rotary  polarization  (right-handed)  with 
true  coniine  (64,  12).  He  had  accomplished  the  SYNTHESIS 
OF  AN  ALKALOID,  the  first  on  record. 

12.  PHENYLHYDRAZINE  Ph.  HN.NH2  is  now  an  important 
reagent  for  aldehydes  and  sugars.  It  is  made  from  aniline  by 
a somewhat  complex  process.  It  is  a colorless  oil  (G  1.19)  of 
a peculiar  odor,  solidifying  to  tabular  crystals  that  fuse  at 
17,  5.  It  forms  a hydrate  melting  at  24.  The  liquid  turns 
brown  on  exposure.  Its  crystallized  hydro  chloride  keeps 
well.  One  part  hereof  dissolved  with  one -and -a- half  parts 
of  sodium  acetate  in  8 to  10  parts  of  water  is  the  glucose 
reagent  used. 


89.  COMPLEX  COMPOUNDS. 

1.  In  my  PRINCIPLES  OF  CHEMISTRY  AND  MOLECULAR 
Mechanics,  published  a quarter  century  ago,  the  chapter  on 
complex  compounds  (pp.  88-102)  comprises  mainly  the 
saccharine  bodies,  the  alkaloids  and  the  albuminoids.  The 
structure  of  these  compounds  has  been  greatly  cleared  up  dur- 


COMPLEX  COMPOUNDS. 


343 


ing  the  interval;  even  the  albuminoids  have  yielded  to  the 
labors  of  Schutzenberger,  of  Paris. 

Beholding  the  infinite  extent  of  this  branch  of  chemistry, 
and  overcome  by  the  difficulty  of  giving  a reasonably  fair  con- 
ception thereof  to  the  mind  of  my  reader  or  hearer,  within  the 
narrow  limits  of  the  chapter  or  the  hour,  I select,  as  only  sub- 
ject for  this  lesson,  the  cup  that  cheers  but  does  not  inebriate. 
Cd,  4. 

2.  More  than  five  hundred  million  pounds  of  dried  TEA 
LEAVES  are  used  by  man  every  year,  and  the  weight  of  COFFEE 
BEANS  consumed  is  very  much  greater  still.  In  South 
America,  MATE  and  GUARANA  correspond  to  tea  and  coffee. 
The  KOLA  nut  of  Africa  has  similarly  been  used  and  has  now 
found  its  way  to  us.  Why  do  millions  of  men,  in  all  climes, 
labor  to  enjoy  a cup  of  these  drinks.?  And  what  about  the 
drink  of  the  old  Mexicans  that  inspired  Linn^us  to  name  the 
tree  THEOBROMA.? 

3.  When  Sertuerner  had  succeeded  to  extract  the  active 
principle  of  opium  (64,  7-8),  chemists  began  their  investiga- 
tion of  the  question  just  asked.  The  answer  is  not  yet  com- 
plete; but  the  researches  undertaken  and  the  results  obtained 
are  so  characteristic  of  the  CHEMISTRY  OF  COMPLEX  COM- 
POUNDS that  we  shall  restrict  ourselves  here  to  this  single 
topic. 

Runge  (1820)  extracted  the  active  principle  of  coffee,  the 
glistening,  acicular  crystals  of  CAFFEINE.  Robiquet,  Pelletier 
and  Caventou  produced  the  same  substance  about  the  same 
time.  In  1827,  Oudry  extracted  the  active  principle  of  tea, 
and  called  it  THEINE.  In  1840,  Martins  found  caffeine  in 
Guarana,  and  Stenhouse  found  (1843)  theine  in  mate.  Lam- 
padius  found  in  cacao  a substance  similar  to  caffeine  (Ber- 
zelius) ; it  is  now  called  THEOBROMINE. 

While  extracted  like  alkaloids,  these  three  substances  are 
not  poisonous  and  not  strictly  alkaloids;  at  least  they  are  not 
precipitated  by  the  general  alkaloid  reagents.  They  are 
largely  combined  with  tannin — especially  jn  tea.  When  the 


344 


LECTURE  89. 


hot  aqueous  extract  is  precipitated  by  basic  lead  acetate,  the 
excess  of  lead  separated  from  the  filtrate  by  hydrogen  sulphide, 
and  the  liquid  carefully  evaporated  to  dryness,  hot  alcohol  will 
extract  the  alkaloidal  substances  in  question  and  leave  them  in 
crystal  form. 

4.  The  noted  Dutch  chemist,  Mulder,  showed  (1838)  that 
THEINE  AND  CAFFEINE  ARE  IDENTICAL  bodies  in  every 
respect.  If,  as  some  contend,  tea  is  a protestant  and  coffee  a 
catholic  drink,  the  difference  must  reside  in  associate  materials 
and  not  in  the  essential  or  active  principles  of  these  substances 
which,  like  the  fundamental  principles  of  religion,  are  the  same 
in  both. 

Chemists  were  treated  to  another  surprise  when  THEO- 
BROMINE, by  treatment  with  methyliodide  in  the  autoclave, 
was  CONVERTED  INTO  THEINE,  which  thus  appears  as 
methyl -theobromine.  This  change  was  already  indicated  by 
the  elementary  analysis,  which  had  given,  for  theobromine 
C7  Hg  N4  O2  and  for  theine  (caffeine)  C Hi©,  N4  O2.  The 
excess  CH2  points  to  the  additional  link  or  methyl. 

5.  When  either  of  these  active  substances  of  tea,  coffee  or 
chocolate  is  heated  on  the  water  bath  with  a strong  oxidizer 
(nitric  acid,  chlorine  water)  to  dryness,  a yellowish  residue 
remains,  which  dissolves  in  the  least  possible  amount  of 
ammonia  with  a beautiful  purple  color.  But  this  is  the  familiar 
MUREXIDE  TEST,  commonly  used  for  the  identification  of 
uric  acid. 

6.  URIC  ACID,  being  slightly  soluble  in  water,  gradually 
separates  from  urine  in  crystals  of  characteristic  forms,  upon 
the  addition  of  the  very  soluble  muriatic  acid.  By  dissolving 
the  reddish  crystals  in  alkali,  discoloring  with  bone  black,  and 
reprecipitating  by  a soluble  acid,  we  obtain  uric  acid  in 
beautiful,  colorless  rhombic  crystals.  It  is  insoluble  in  alcohol 
and  ether,  difficultly  soluble  in  water  (1  in  15,000).  This 
lack  of  solubility  causes  gouty  and  rheumatic  troubles. 
Piperazine  is  the  best  internal  solvent  for  uric  acid. 


COMPLEX  COMPOUNDS. 


345 


7.  MUREXIDE  is  ammonium  purpurate.  With  one  atom  of 
water  it  forms  quadratic  crystals  [C5  H4(NH4)N5  O0  + H2O] 
reflecting  golden  and  greenish  colors  in  sun  light  and  dissolv- 
ing in  water  to  a rich  purple  color.  It  has  been  extensively 
used  as  a dye.  Boiling  destroys  it  under  evolution  of  ammonia 
gas.  Guano,  being  largely  uric  acid  and  urates,  permits  the 
preparation  of  murexid  in  quantity. 

In  the  extract  of  tea 
leaves  we  find  a corre- 
lated nitrogenous  body, 
which  does  not  show  the 
murexid  reaction,  but  in- 
stead gives  the  XANTHIN 
reaction.  That  is,  when 
evaporated  with  nitric  acid 
to  dryness,  it  turns  YEL- 
LOW to  yellowish  red  with 
potassa,  and  thereafter 
purplish  on  heating.  The 
same  substance,  Xanthin, 
occurs  inthe  animal  system. 
Its  formula  is  C5  H4  N4  O2, 
that  of  uric  acid  being 
C5  H4  N4  O3.  The  latter 
seems  to  be  an  oxide  of  the 
former. 

8.  Comparing  THE  MOLECULAR  FORMULyE  of  the  four 
compounds  before  us,  and  simply  giving  the  number  of  atoms 
of  C,  H,  N,  O invariably  in  this  order,  we  find:  Uric  acid, 
5,  4,  4,  3;  Xanthin,  5,  4,  4,  2;  Theobromine,  7,  8,  4,  2; 
Theine,  8,  10,  4,  2.  Accordingly,  uric  acid  might  be  oxidized 
Xanthin.  Theobromine  contains  2 CH2  and  Theine  3 CH2 
more  than  Xanthin. 

9.  Long-continued  and  difficult  chemical  researches,  both 
analytical  and  synthetical,  have  shown  these  substances  to  be 
actually  related  in  that  way.  Analytically,  all  THESE  COM- 


.#  = ►. 


o-i 


►o 


< 

'•  CL 

Aantfun. 


> « ^>=0 

o--#:  #-4 

► I 

* ® LiTtcAcid. 

O 


-346 


LECTURE  89. 


POUNDS  YIELD  UREA  H2N— CO— NH2 ; in  fact,  each  yields 
two  molecules  per  atom  when  completely  broken  up.  Accord- 
ingly, each  one  of  these  four  substances  contains  two  nuclei 
of  urea.  Synthetically,  the  three  bodies  have  now  all  been 
made  from  Xanthin. 

10.  One  of  the  four  urea  nuclei  (the  one  to  the  right  in  the 
diagrams)  is  split  off  much  more  readily  than  the  other;  the 
two  are  therefore  not  tied  or  bound  in  the  same  manner.  In 
many  cases — such  as  the  oxidation  in  the  murexid  test — the 
other  urea  nucleus  (to  the  left)  remains  united  with  a group 
C3  to  ALLOXAN.  This  Group  C3  is  separated  as  mesoxalic 
acid  C3  H2O5  when  alloxan  is  boiled  with  baryta  water. 

11.  Emil  Fischer,  of  Berlin,  has  completed  the  synthesis 
of  these  substances  (Naturw- Rundschau,  1896,  p.  245)  in 
conformity  with  the  results  of  decomposition  here  indicated. 
His  investigations  are  expressed  in  the  graphical  formulae 
here  inserted.  These  diagrams  have  been  constructed  accord- 
ing to  the  developed  structural  formula  published  by  him. 
Theobromine  is  dimethylxanthin,  the  methyl  CH3  taking  the 
places  of  hydrogen  at -a  and  b.  Theine  is  trimethylxanthin, 
containing  an  additional  methyl  instead  of  the  hydrogen 
atom  at  c. 

12.  And  now,  DO  WE  UNDERSTAND  THE  CRAVING  OF 
MAN  FOR  TEA,  COFFEE  AND  CHOCOLATE.?  By  no  means. 
But  we  have  seen  how  complex  organic  compounds  are  being 
taken  to  pieces,  and  built  up  again.  Also,  how  a small 
amount  of  certain  substances  may  exert  great  influence  on  the 
body  and  how  near  the  most  refined  food  approaches  some  of 
the  waste  products  of  the  system.  Do  they  perform  the 
function  of  the  lubricant  in  the  humon  machine.?  The  deeper 
we  search,  and  the  more  we  learn,  the  greater  becomes  the 
mystery  to  the  thinker.  Every  question  answered  raises  at 
least  one  new  question,  more  profound  and  much  more  dilficult 
than  the  one  just  answered. 


90.  ORGANIC  SYNTHESIS. 


1.  In  this  lesson  we  reach  THE  PRESENT  BOUNDARY  OF 
CHEMISTRY.  We  have  begun  our  course  with  the  prime 
materials  furnished  by  plant  and  animal.  We  have  extracted 
the  pure  chemical  compounds  thereof.  We  have  changed  and 
transformed  these  in  many  ways.  We  have  been  enabled  to 
learn  much  of  the  intimate  structure  of  these  bodies. 

2.  Chemists  have  produced  NEW  SUBSTANCES,  con- 
structed on  exactly  the  same  plan  as  these  organic  substances, 
but  such  as  nature  never  had  produced  because  they  cannot 
even  exist  under  ordinary  conditions.  The  chemist  had  not 
only  to  create  these  compounds,  but  also  to  protect  them 
against  surrounding  nature.  We  refer  to  the  ORGANO- 
METALLIC  COMPOUNDS. 

3.  Bunsen’s  researches  (1842)  on  arsenic  radicals  (cacodyl, 
— As  Me2,  monovalent)  opened  this  field.  Frankland  produced 
(1849)  quite  a group  of  simple  ethers  containing  heavy  metals 
instead  of  oxygen,  such  as  zinc  ethyl,  Zn  Et2.  In  1869 
FRIEDEL  began  his  extended  researches,  establishing  a 
CHEMISTRY  OF  SILICON  COMPOUNDS  parallel  to  that  of  the 
carbon  compounds  or  organic  chemistry,  including  silicon 
chloroform  and  ethers,  and  determining  the  true  constitution 
of  all  silicon  compounds,  from  that  of  quartz  onward! 

4.  These  organo-metallic  compounds  almost  invariably 
BURN  IN  CONTACT  WITH  THE  ATMOSPHERE.  They  have 
to  be  prepared  and  maintained  in  an  artificial  atmosphere  free 
from  oxygen.  Their  preparation  is  both  DIFFICULT  AND 
DANGEROUS.  The  lessons  they  have  taught  are  most 
important.  See  my  paper  on  Central  Substitution,  Comptes 
Rendus,  T.  115,  p.  314;  1892. 

5.  In  the  chemical  changes  of  true  organic  compounds, 
that  is,  such  as  have  been  extracted  from  vegetable  and 
animal  materials,  as  well  as  in  the  formation  of  organo- 
metallic  compounds,  no  really  new  reactions  have  been  resorted 


348 


LECTURE  90. 


to  or  discovered.  ALL  ORGANIC  CHEMICAL  REACTIONS 
ARE  IN  NO  MANNER  DIFFERENT  FROM  THOSE  OF  INOR- 
GANIC CHEMISTRY.  The  forces  brought  into  play  being  less, 
and  the  compounds  being  generally  more  complex,  greater 
delicacy  in  the  chemical  operations  is  ordinarily  essential  to- 
success. 

6.  Hence  it  would  seem  that  any  true  organic  compound,, 
as  produced  in  the  living  plant  or  animal,  ought  to  be  pro- 
ducible in  the  chemical  laboratory  by  SYNTHESIS  FROM 
INORGANIC  MATERIALS,  provided  the  chemist  be  skillful 
enough  and  provided  he  possess  sufficient  knowledge.  But  as  a 
matter  of  fact,  no  truly  organic  compound  had  been  produced  by 
synthesis  from  the  elements  up  to  the  middle  of  this  century. 

7.  At  that  time  LIEBIG  was  considered  the  leading  chemist 
of  the  world.  In  his  “Chemical  Letters”  of  1844  he 
DECLARED  IT  IMPOSSIBLE  to  produce  any  organic  compound 
from  the  constituent  elements.  These  letters  had  a wide  cir- 
culation in  all  countries,  having  been  translated  into  most 
languages. 

8.  Liebig  was  well  aware  that  his  friend  and  oft-time  co- 
laborer Woehler  had  produced  (1828)  UREA  from  inorganic 
materials  (84,  4).  This  compound  was,  however,  looked 
upon  as  an  organic  waste  product  merely;  besides,  the 
cyanogen  compounds  used  in  the  transformation  might  be  con- 
sidered either  organic  or  inorganic  themselves. 

9.  Liebig’s  declaration  would  have  been  in  exact  accord- 
ance with  fact,  if  he  had  said  it  was  “impossible  for  him”' 
to  produce  organic  compounds  by  synthesis  from  the  elements. 
He  erred  in  assuming  that  what  was  impossible  for  him  would 
also  be  impossible  for  all  other  chemists,  and  forever! 

10.  The  man  who  was  soon  to  do  what  Liebig  declared  an 
absolute  impossibility  was  already  studying  chemistry  at  Paris. 
Six  years  later  he  became  attached  to  the  College  de  France 
as  an  assistant.  Ten  years  after  the  declaration  of  Liebig,  he 


ORGANIC  SYNTHESIS. 


349 


had  accomplished  one  of  the  impossibilities  of  Liebig,  the  syn- 
thesis of  the  fats  (78,  12) . In  1860,  the  Impossibility  of  Liebig 
was  replaced  by  BERTHELOT’S  ORGANIC  CHEMISTRY 
FOUNDED  ON  SYNTHESIS. 

This  work  has  so  completely  changed  the  aspect  of  chemical 
science,  that  it  is  unnecessary  to  enter  upon  details.  His 
method  of  operation,  as  well  as  of  thought,  have  become  part 
of  the  science.  A most  fascinating  exposition  thereof  has 
been  given  by  Berthelot  himself  in  his  CHEMICAL  SYNTHESIS, 
Paris,  1876;  a volume  forming  part  of  the  International  Scien- 
tific Library. 

11.  The  most  brilliant  work  of  chemical  synthesis  done  in 
Germany  has  been  accomplished  by  EMIL  FISCHER,  now  at 
the  University  of  Btrlin.  His  discovery  of  the  reaction  of 
glucose  on  phenylhydrazin  (88,  12)  furnished  him  the  instru- 
ment that  lead  to  THE  SYNTHESIS  OF  ALL  THE  SUGARS. 
His  admirable  work  on  uric  acid  and  the  allied  compounds  has 
been  considered  in  our  preceding  lesson. 

12.  And  now— WILL  SYNTHESIS  FROM  INORGANIC 
MATERIALS  EVER  DO  AWAY  WITH  OUR  DEPENDENCE  ON 
THE  CELL-LABORATORY  OF  PLANT  AND  ANIMAL.?  In  cer- 
tain special  lines,  yes;  on  the  whole,  most  likely  an  emphatic 
no.  The  plants  are  greater  “specialists”  than  our  chemists 
ever  are  likely  to  be.  The  power  they  use  is  the  cheapest  of 
all,  and  the  best;  it  is  the  glorious  sunshine  that  fills  the 
world  so  long  as  man  shall  live  on  earth — for  he  will  have  to 
die  when  the  sun  shall  begin  to  grow  dim.  The  raw  materials 
of  the  cell-chemists  are  also  the  cheapest  of  all,  namely  rain 
and  air.  To  give  plants  the  best  chance  to  furnish  us  the 
highest  possible  returns,  we  should  work  with  our  hands  in 
field  and  garden,  should  plow  and  plant,  harrow  and  hoe,  in 
order  that  we  may  glean  and  garner  for  self  and  others,  for 
home  and. market.  And  as  in  this  labor  we  come  in  touch 
with  Mother  Earth,  and  draw  deeply  the  air  just  purified  by 
that  beam  of  power  from  Father  Sun,  we  become  strong  in 
body,  and  pure  in  heart,  while  our  soul  is  filled  with  Peace 
and  Faith  and  Hope. 


91.  THE  ATOM-WORLD. 


1.  “Let  us  remember,  please,  that  the  search  for  the 
constitution  of  the  world  is  one  of  the  greatest  and  noblest 
problems  presented  by  Nature.”  This  word  of  GALILEO, 
taken  from  his  second  dialogue  on  the  Systems  of  the  World, 
we  have  placed  as  motto  on  the  front  page  of  this  book. 

2.  The  Great  World,  the  MACROCOSMOS  of  the  Ancients, 
was  but  the  flat  earth,  surrounded  by  the  sea,  and  lit  up  by 
sun  and  stars.  To  Modern  Science  it  is  the  wonderful,  infinite 
All,  in  which  the  earth  is  but  an  atom.  The  mechanical 
structure  of  this  world  Galileo  had  in  mind.  He  most  success- 
fully assisted  in  the  search  for  its  constitution;  and  was 
rewarded  by  persecution,  prison  and  torture. 

3.  To  the  searching  eye  of  Science,  the  atom  itself  becomes 
a world;  -tit  is  the  true  MICROCOSMOS.  The  search  of  its 
constitution  offers  no  less  great  and  noble  a problem  than  that 
of  macrocosmos.  With  thermometer  and  goniometer  we  have 
learned  to  measure  the  dimensions  of  the  atoms,  precisely  as 
astronomers  measure  the  dimensions  of  the  planets  with 
pendulum  and  theodolite.  C.  R.,  T.  76,  p.  1594;  1873. 

4.  The  guiding  rule  in  this,  our  study  of  microcosmos,  is 
the  same  that  has  laid  open  the  constitution  of  macrocosmos: 
it  is  MECHANICS,  the  mathematical  expression  of  the  action 
of  matter  through  space.  This  action  is  independent  of  the 
absolute  dimensions.  The  laws  of  motion  apply  equally  to 
large  and  small  objects.  The  planet  is  but  an  atom  in  the 
world;  the  silicon  atom  is  half  the  world  in  quartz. 

5.  The  science  of  mechanics  was  founded  by  ARCHIMEDES, 
of  Syracuse,  twenty-five  centuries  ago.  He  established  the 
laws  of  statics,  the  science  of  equilibrium.  GALILEO  (p.  18) 
laid  the  foundations  of  dynamics,  the  science  of  motion. 
HUYGHENS  (p.  20)  worked  out  the  laws  of  rotations  and  revo- 


THE  ATOM-WORLD. 


351 


lutions.  From  NEWTON’S  Principia  to  LAPLACE’S  Celestial 
Mechanics,  this  search  for  the  constitution  of  macrocosmos  has 
been  perfected. 

6.  The  beginning  of  the  mechanics  of  microcosmos  may  be 
traced  back,  even  to  Galileo  himself.  About  the  middle  of 
this  century  the  MECHANICAL  CONSTITUTION  OF  THE 
GASES  seemed  to  open  the  field  anew.  But  to  the  mathe- 
matician, the  molecule  remained  merely  an  elastic  ball,  while 
the  chemist,  dripping  with  tar,  made  flat  diagrams  of  com- 
plex molecules  in  utter  disregard  of  the  laws  of  mechanics 
which  he  did  not  care  to  know. 

7.  The  extreme  one-sidedness  of  German  chemistry  of  the 
present,  which  has  compelled  the  government  to  fill  the  two 
principal  chemical  professorships  in  Germany  with  a Russian 
and  a Hollander,  is  also  noted  in  the  SENSATIONAL  DECLA- 
MATIONS of  one  of  their  most  voluminous  writers  against  the 
great  masters  of  mechanical  science,  from  Newton  to  Laplace, 
and  his  habitual  derision  of  mechanical  conceptions  in  chemical 
research. 

8.  We  would  take  no  notice  of  these  strange  declamations 
if  they  were  not  taken  as  representing  that  GERMAN  SCIENCE 
WHICH  THE  WORLD  JUSTLY  REVERES.  Unmindful  of 
Liebig’s  equally  unfounded  authoritative  declaration  of  the 
impossibility  of  the  true  synthesis  of  genuine  organic  com- 
pounds, young  Berthelot  performed  these  syntheses  from  the 
elements.  In  the  same  manner,  the  author  has  continued  to 
establish  the  constitution  of  compounds  by  applying  the 
mechanics  of  Galileo,  Huyghens,  Newton  and  Laplace  though 
these  masterminds  are  denounced  by  the  chemists  of  the 
University  of  Leipzig  who  writes  so  much  that  his  thoughts 
evidently  cannot  keep  up  with  his  pen.  See  my  True  Atomic 
Weights,  pp.  42—46;  1894. 

9.  In  the  gaseous  state,  the  molecules  move  freely  in  space 
until  they  hit  the  walls  of  the  containing  vessel  or  another 
particle.  The  flight  of  the  gaseous  molecule  is  free,  unre- 


352 


LECTURE  91. 


strained,  like  the  motion  of  a projectile  or  that  of  a cosmical 
body.  The  motion  of  the  gaseous  molecules  therefore  must 
conform  to  the  established  LAWS  OF  FREE  MOTION. 

10.  The  motion  of  projection  or  translation  is  associated 
with  a rotation  around  one  of  the  permanent  axes.  For  one  of 
these  axes,  the  moment  of  inertia  (mass)  is  greatest,  for  the 
other  it  is  smallest.  In  continued  motion,  the  body  will  neces- 
sarily come  to  rotate  about  the  first  of  these  axes,  it  being  the 
most  stable.  IN  THE  GASEOUS  STATE  THE  PARTICLES 
(MOLECULES)  HAVE  A MOTION  OF  TRANSLATION  AND 
ROTATE  AROUND  THEIR  SHORTEST  AXIS  (i.  e.,  the  perma- 
nent axis  for  which  the  moment  of  inertia  is  the  greatest). 

11.  This  is  the  motion  of  all  the  cosmical  bodies.  These 
motions  are  best  shown  by  the  BOOMERANG.  Small  card 
boomerangs  allow  the  instructive  and  elegant  lecture  experi- 
ment, the  two  motions  being  readily  seen  by  all.  The  experi- 
menter, after  a little  practice,  needs  only  one  boomerang, 
since  it  promptly  returns  to  him  every  time.  By  attaching 
balls,  chain,  hoop,  flask  with  water  and  colored  ether,  or  water 
and  mercury,  to  a catgut  string,  and  rapidly  TWIRLING  the 
upper  end  hereof,  the  rotation  will  be  final  around  the  shorter 
axis,  i.  e.,  the  one  for  which  the  moment  of  inertia  is  greatest. 

12.  In  the  SOLID  STATE,  particles  merely  oscillate.  MELT- 
ING, THEY  BEGIN  TO  ROTATE,  necessarily  AROUND  THEIR 
LONGEST  AXIS,  being  their  axis  of  minimum  moment  of 
inertia.  Fleated  high  enough,  particles  will  finally  be  pro- 
jected from  the  surface  of  the  liquid,  and  move  freely  through 
space  as  just  described.  This  MECHANICAL  DESCRIPTION 
OF  THE  THREE  STATES  OF  AGGREGATION  the  author  has 
published  a quarter  of  a century  ago,  and  proved  it  to  be  true 
by  many  deductions,  a few  of  which  will  now  be  given. 


92.  PRISMATIC  ATOMS  AND  BOILING. 


1.  AT  THE  BOILING  POINT,  the  particles  are  projected 
from  the  liquid  in  numbers  sufficient  to  BALANCE  THE 
PRESSURE  OF  THE  ATMOSPHERE.  At  the  same  pressure, 
all  boiling  liquids  are  necessarily  in  corresponding  condition. 
We  need,  to  connect  them,  only  to  study  the  relation 
between  pressure  and  boiling  point  for  any  one  liquid. 
C.  R.,  T.  112,  p.  998;  1891. 

2.  To  study  the  FORM  OF  ATOMS,  it  is  necessary  to  begin 
with  groups  of  bodies  known  to  be  of  the  same  kind.  Such 
groups  we  have  in  the  HOMOLOGOUS  SERIES  of  modern 
organic  chemistry.  Any  given  alcohol  radical  R added  to 
— CH2.H  forms  a paraffin;  to  — CH2.OFI  an  alcohol; 
to  — CO.H  an  aldehyde;  to  — CO. OH  an  acid;  to  — CH2.CI 
a chloride,  etc.,  etc.  Lecture  87. 

3.  Let  us  compare  say  the  HOMOLOGOUS  ALCOHOLS, 
wherein  R = Cm  H2m+i.  In  all  these  compounds,  the  active 
terminal,  i.  e.  that  part  which  can  react  chemically,  is  the 
same,  namely  — CH2.OH.  It  weighs  31.  The  other  part 
Rm  may  be  written  H + m (CH2).  The  entire  alcohol 
atom  therefore  weighs  32-{-14m,  where  m is  the  total  number 
of  carbon  atoms  less  one. 

4.  All  the  OTHER  HOMOLOGOUS  SERIES  mentioned  may 
be  expressed  by  corresponding  formulae.  The  paraffins  by 
14+14m.  The  aldehydes  by  30-(-14m.  The  acids  by  46+14m. 
The  chlorides  by  48.5+14m.  The  bromides  by  93+14m. 
The  cyanides  by  49+14m.  The  amines  by  31+14m. 

5.  These  substances  can  be  readily  changed  chemically 
one  into  the  other — both  by  changing  the  radical  of  m links 
CH2  and  especially  by  changing  the  active  terminal.  It  may 
not  be  elegant,  but  it  certainly  is  very  correct,  to  compare  the 
TERMINAL  to  the  head,  the  RADICAL  to  the  vertebrae  of  an 
animal— say  a snake.  The  carbon  of  the  link  CH2  would  rep- 
resent the  vertebra,  the  two  hydrogens  the  ribs  attached  thereto. 


354 


LECTURE  92. 


6.  Now  all  chemists  agree  that  these  CHa  are  joined  each 
way  by  a simple  link  or  valence.  But  how  is  the  form  of  the  en- 
tire radical:  rigid,  forming  a STRAIGHT  LINE,  or  spiral  like  a 
CORKSCREW  (86,  4 to  6) . Our  great  German  chemists  do  not 
know,  and  therefore  declare  this  question  is  insoluble,  and 
should  not  be  approached.  This  admirable  system  throws  odium 
on  anyone  who  dares  to  attempt  the  solution  of  such  a question. 
They  even  excuse  Berzelius  (E.  Meyer,  History,  p.  238,  Engl, 
edition  1891)  from  having  thought  such  a problem  soluble. 

7.  But  reading  our  GRAND  MASTER  once  again  (91,  1) 
we  venture  to  tread  where  der  Herr  Geheimrath  has  not 
been.  We  put  the  question  once  more  clearly  before  our 
eyes:  do  these  m -links  of  the  radical  of  modern  chemists 
form  a rigid,  straight  line,  or  do  they  not. 

8.  Now,  nature  has  the  rather  human  habit  of  giving  A 
PLAIN  ANSWER  TO  A PLAIN  QUESTION;  but,  at  the  same 
time,  she  only  answers  yes  or  no,  and  thus  gives  us  no 
answer  at  all  unless  we  have  taken  the  trouble  to  learn  how 
to  ask  the  question.  Really,  the  main  difficulty  of  investiga- 
tion is  to  learn  to  ask  the  question.  That  is  a mental  problem. 
Our  apparatus  cannot  help  us  therein. 

9.  Now  TWO  LINKS  CH2  form  a straight  line;  for  two 
points  determine  such  a line.  These  two  points  are  the 
centers  of  gravity;  weight  14  each.  Let  their  distance  be 
taken  as  unity.  The  moment  of  inertia  of  this  2 CH2  will 
then  be  7 exactly.  If  the  radical  forms  a straight  line,  the 
moment  of  inertia  for  3 links  CH2  will  be  28,  for  5 links  will 
be  112,  for  7 links  364,  for  9 links  812,  and  so  forth.  The 
moment  of  inertia  is  the  sum  of  the  each  weight  into  the 
square  of  its  distance  from  the  axis,  here  the  center  of  gravity 
or  the  middle  atom. 

10.  According  to  91,10,  THE  BOILING  POINT  must  be 
some  function  of  this  moment  of  inertia.  If  the  form  of  the 
radical  be  not  straight,  the  moments  of  inertia  will  increase  at 
a much  less  rapid  rate;  that  popular  tetrahedral -corkscrew 
would  show  very  slowly  growing  moments  of  inertia  for  in- 
creasing values  of  m.  On  plates  76  and  77  we  have  copied  the 


PRISMATIC  ATOMS  AND  BOILING. 


355 


graphical  representation  of  the  facts  observed  (boiling  points) 
and  our  function  of  the  moments  of  inertia  (simply  related  to 
the  logarithm  of  number  of  carbon  atoms).  See  note  on 
logarithm  below. 

11.  The  most  NECESSARY  DATA  have  been  given  in  our 
papers  kindly  presented  by  Berthelot  to  the  Academy  of 
Sciences  of  Paris,  and  inserted  in  full  in  the  Comptes  Rendus 
of  that  Academy  for  1892.  Plates  76  and  77  are  simply 
re-prints  from  the  Comptes  Rendus.  The  very  curves,  how- 
ever, suffice  to  give  the  answer,  without  entering  upon  the 
details  of  calculation,  the  leading  formulae  for  which  are 
inserted  on  the  plates. 

12.  The  answer  to  the  question  is  complete  and  decisive. 
The  alcoholic  radical  Cm  Rm+i  forms  a straight  line,  so  far  as 
the  maximum  moment  of  inertia  is  concerned.  ALL  SATU- 
RATED ALCOHOLIC  COMPOUNDS  ARE  LINEAR,  consisting 
of  the  rectilinear  tail  or  series  of  CH2  links  and  terminating 
in  the  head  chemically  characterizing  the  compound  as 
paraffin,  acid,  chloride,  and  the  like. 


Note. — The  log  n of  our  plates  means  the  logarithm  of  the  total 
number  n of  carbon  atoms  of  the  compound.  The  actual  values,  taken 
from  any  logarithm  table,  are  given  below: 


No. 

Log. 

No. 

Log. 

No. 

Log. 

No. 

Log. 

No. 

Log. 

10 

1. 000 

20 

1. 301 

30 

1.477 

40 

1.602 

I 

0.000 

1 1 

1. 04 1 

21 

1.322 

31 

1. 491 

41 

1.613 

2 

0.301 

12 

1.079 

22 

1.342 

32 

1-505 

42 

1.623 

3 

0.477 

13 

1.114 

23 

1.362 

33 

1-519 

43 

1.634 

4 

0.602 

14 

1.146 

24 

1.380 

34 

1-532 

44 

1.644 

5 

0.699 

15 

1.176 

25 

1.398 

35 

1-544 

45 

1-653 

6 

0.778 

16 

1.204 

26 

I -415 

36 

1-556 

46 

1.663 

7 

0.845 

17 

1.230 

27 

1-431 

37 

1.568 

47 

1.672 

8 

0.903 

18 

1-255 

28 

1.^47 

38 

1.580 

48 

1. 681 

9 

0-954 

19 

1.279 

29 

1.462 

39 

I -591 

49 

1.690 

Such  a table  of  logarithms  can  be  obtained  bv  noting  the  consecutive 
excursions  of  the  pointer  of  a fine  chemical  balance  during  ten  to  thirty 
minutes.  The  number  of  the  oscillation  and  the  corresponding  excursion 
form  the  logarithmic  curve. 

. We  here  have  referred  to  the  normal  compounds  exclusively.  We  also 
designedly  have  taken  the  weight  instead  of  the  mass  in  the  moments  of 
inertia,  for  obvious  reasons. 


93.  ATOM  LINKAGE  AND  FUSING. 


1.  Having  determined  the  atoms  of  all  alcoholic  serials  to 
be  rectilinear,  so  far  as  the  arrangement  of  the  centers  of 
gravity  of  their  links  CH2  is  concerned,  the  next  question  is, 
how  are  the  carbon  atoms  linked? 


2.  The  rectilinear  form  established  leaves  only  TWO  POS- 
SIBLE MODES  OF  LINKAGE  of  the  carbon  atoms  in  the  alco- 
holic radical.  The  carbon  atoms  may  link  end-to-end,  or 
face-to-face.  That  is,  since  they  have  some  form,  say  like  a 
watch,  they  may  attract  end-to-end,  or  face-to-face. 

3.  In  the  END-TO-END  POSITION  the  carbon  atoms 
could  revolve  and  the  hydrogen  atoms  of  CH2  might  face  any 
direction.  The  resulting  compound  would  be  far  from  rigid. 
Yet  we  have  the  best  of  reasons  to  suppose  that  element 
atoms  in  compound  atoms  are  held  rigidly  in  place,  like  mole- 
cules in  a crystal.  The  end-to-end  position  is  therefore  not 
probable,  a-priori. 

4.  In  the  FACE-TO-FACE  POSITION  of  the  carbon  atoms, 
the  structure  would  be  rigid,  the  hydrogen  would  alternately 
turn  as  the  carbon  does.  The  entire  atom  would  be  most 
symmetric  as  well  as  rigid.  This  is  a-priori  the  most  probable 
method  of  linkage  of  the  carbon  atoms  in  alcoholic,  and  in 
fact,  in  all  organic  compounds. 


5.  Let  us  again  submit  the  question  to  nature,  and  first 
formulate  the  most  probable  case.  The  carbon  atoms  would 
occupy  positions  as  the  types  here  printed.  The  points  of 

attraction  of  atoms  A,  C,  E, 


C 


G 


etc.  would  be  directed  down- 
ward towards  the  correspond- 
ing points  of  B,  D,  F,  etc., 
directed  upwards. 


ATOM  LINKAGE  AND  FUSING. 


357 


6.  IF  THE  TOTAL  NUMBER  OF  ATOMS  OF  CARBON  BE 
EVEN,  the  axis  containing  the  center  of  gravity  of  the  com- 
pound will'  run  exactly  midway  between  the  two  lines.  If 
the  distance  be  called  2,  the  moment  of  inertia  will  be  simply 
equal  to  the  atomic  weight,  the  distances  of  all  atoms  from  the 
axis  being  unity. 

7.  BUT  IF  THE  TOTAL  NUMBER  OF  CARBON  ATOMS 
BE  ODD,  the  result  will  be  entirely  different.  Suppose  we 

have  three  atoms  only.  In  that  case 
A C the  center  of  gravity  evidently  is  much 

a nearer  the  two  atoms  A and  C than  the 

single  atom  B.  In  fact,  everyone  under- 
stands the  space  is  divided  as  one  to  two.  The  distance  from 
the  geometrical  middle  to  the  real  axis  is  one -third  unit. 

8.  If  the  total  number  be  five  atoms  of  carbon,  the  four 
will  balance  exactly.  But  the  fifth  will  evidently  draw  the 

center  of  gravity  one -fifth  unit  up  from 
ACE  the  middle  line.  That  is,  the  perma- 
a Q nent  axis  of  rotation,  which  passes 

through  the  center  of  gravity  of  the 
system,  lies  one-fifth  unit  of  distance  away  from  the  geomet- 
rical axis  or  middle  line.  For  seven  atoms  it  will  be  one- 
seventh,  and  so  forth. 

9.  Now  it  is  a simple  principle  in  mechanics,  that  the 
moment  of  inertia  of  any  body,  or  system  of  bodies,  is  smallest 
for  the  axis  passing  through  the  center  of  gravity.  For  ANY 
Axis  at  any  distance  PARALLEL  to  the  first  axis,  the  moment 
is  greater  by  a quantity  proportional  to  the  SQUARE  of  this 
distance. 

10.  Consequently,  the  moment  of  inertia  for  the  alcoholic 
serial  compounds  considered,  in  reference  to  the  permanent 
axis  parallel  to  the  length  of  the  system,  increases  proportional 
to  the  total  atomic  weight  of  the  entire  system;  but  for  com- 
pounds of  an  ODD  NUMBER  N OF  CARBON  ATOMS  the 
moment  of  inertia  is  diminished  by  a quantity  proportional  to 
the  square  of  one -nth  of  the  total  number  of  carbon  atoms. 


358 


LECTURE  93. 


11.  But  this  moment  of  inertia  determines  the  fusing  point 
of  compounds  (91,  12).  Hence  the  FUSING  POINT  OF  ALCO- 
HOLIC SERIALS  IS  SMALLER  FOR  COMPOUNDS  HAVING  AN 
ODD  NUMBER  OF  CARBON  ATOMS,  THAN  FOR  THOSE 
HAVING  AN  EVEN  NUMBER  of  carbon  atoms;  the  difference, 
being  inversely  proportional  to  the  square  of  the  number  of 
carbon  atoms,  will  rapidly  diminish  as  n increases  and  vanishes 
when  n becomes  sufficiently  large. 

12.  But  this  is  precisely  the  case  for  the  paraffins,  the 
fusing  points  for  which  have  been  presented  in  curves  D and 
C of  Fig.  6,  page  plate  74,  according  to  the  observations  of 
Krafft.  See  for  fuller  data,  Comptes  Rendus,  May  19,  August 
17,  and  November  22,  1891.  HENCE  THE  CARBON  ATOMS 
ARE  JOINED  FACE-TO-FACE  in  the  organic  compounds. 
No  such  marvelous  and  hitherto  utterly  inexplicable  differences 
could  occur  in  the  end-to-end  position  between  compounds 
containing  even  and  odd  numbers  of  carbon  atoms. 


The  Fatty  Acids  show  the  same  differences  in  a most  striking  man- 
ner. These  remarkable  differences  have  puzzled  modern  chemists 
greatly.  The  deductions  given  make  the  determinations  of  the  fusing 
points  an  experimentum  crucis  for  the  linkage  of  the  carbon  atoms,  as 
here  shown. 

For  the  fatty  acids,  the  fusing  points  F and  the  total  number  n of  car- 
bon atoms  are  given  in  the  following  little  table.  It  will  be  noted  that 
the  melting  point  of  the  odd-numbered  acid  is  from  3 to  2 below  that  of 
the  preceding  even-numbered  acid,  while  the  next  even-numbered  acid 
is  from  20  to  6 degrees  higher : 


n 

F 

n 

F 

n 

F 

8 

16.0 

14 

54 

20 

75 

9 

12 

15 

51 

21 

72 

10 

31-4 

16 

62 

22 

78 

1 1 

28 

17 

60 

23 

12 

43-6 

18 

69 

24 

80.5 

13 

40.5 

19 

66.5 

25 

77 

94.  ATOMIC  VOLUME. 


1.  The  atomic  volume  of  any  compound  in  the  solid  or  liquid 
state  is  the  volume,  in  cubic  centimeters,  occupied  by  one 
gramme-atom  of  the  substance.  THE  ATOMIC  VOLUME  OF 
WATER  IS  18;  for  each  cubic  centimeter  of  water  weighs  one 
gramme,  and  the  atomic  weight  of  water  is  18. 

2.  The  specific  gravity  of  any  substance  being  the  weight, 
in  grammes,  of  one  cubic  centimeter  of  that  substance  (2,  11), 
it  follows  that  THE  ATOMIC  VOLUME  IS  OBTAINED  BY 
DIVIDING  THE  SPECIFIC  GRAVITY  OF  THE  SUBSTANCE 
INTO  ITS  ATOMIC  WEIGHT.  For  water,  G is  1,  the  atomic 
weight  18;  hence  the  atomic  volume  is  18  cc  per  gramme-atom. 

3.  Plate  p.  394  gives  the  specific  gravity  for  the  liquid 
PARAFFINS  Cn  H2nX2  from  n 5 to  n = 35.  The  points  con- 
nected by  dots  form  the  SPECIFIC  GRAVITY  CURVE  of  this 
homologous  series.  The  curve  first  rises  rapidly,  then  turns, 
and  from  n = 16  changes  but  very  little.  That  is,  the 
specific  gravity  of  the  higher  paraffins  is  almost  constant. 
They  could  not  be  distinquished  by  their  gravity. 

4.  Figure  5 on  the  same  plate  represents  the  ATOMIC  (or 
molecular)  VOLUME  of  these  paraffins.  It  will  be  noticed  that 
this  curve  is  practically  a straight  line.  Only  for  the  lower 
compounds  (from  5 to  10)  is  the  volume  slightly  in  excess  of 
the  corresponding  points  on  the  straight  line.  For  22  the 
volume  is  400;  hence  practically  18  for  each  link  CH2. 

5.  The  higher  paraffin  atoms  accordingly  occupy  a PRIS- 
MATIC SPACE  equal  to  as  many  times  the  atomic  volume  of 
water  as  the  paraffin  contains  carbon  atoms  or  links  CH2 . The 
very  deviation  for  the  lower  members,  the  author  has  shown 
to  be  due  to  the  two  terminal  hydrogen  atoms,  the  influence 
of  which  rapidly  becomes  insensible  with  the  increase  of  the 
number  of  carbon  atoms.  C.  R.,  T.  113,  p.  37,  Equat.  22;  1891. 


360 


LECTURE  94. 


6.  The  equality  of  the  atomic  VOLUME  OF  EACH  LINK 
CH2  in  paraffins  with  that  of  water  has  also  been  recognized 
by  the  author  fully  thirty  years  ago.  The  atomic  volume  of 
alcohols  and  acids  being  approximately  one  water  volume  in 
excess  of  that  or  the  corresponding  paraffin,  shows  that  the 
terminals  of  — CH2  OH  in  alcohols  and  of  — CO.  OH  in  acids 
make  the  hydroxyl  OH  nearly  equal  to  the  link  CH2. 

7.  Accordingly,  all  these  homologous  serials  may  be  looked 
upon  as  forming  PRISMATIC  ATOMS  of  the  same  cross-section 
(very  nearly),  and  differingonly  in  length.  The  cross-section 
evidently  equals  that  of  the  water  atom,  which  becomes  a 
convenient  unit.  The  cross-section  we  have  called  ATOMARE, 
the  length  ATOMETER  (Atomechanics,  1867).  The  atometer 
of  a paraffin  is  n,  that  of  an  acid  or  alcohol  n + 1,  if  n repre- 
sents the  total  number  of  carbon  atoms,  arranged  in  a single 
straight  line  (normal). 

8.  THE  ATOMIC  VOLUME  of  homologous  series  MAY  BE 
CALCULATED  by  two  methods,  namely,  the  statical  and  the 
dynamical  method  (C.  R.,  T.  113,  p.  36;  1891).  In  the 
STATICAL  METHOD,  the  volume  of  the  atomic  prism  is 
determined  from  its  section,  which  is  constant  in  the  same  and 
correlated  series,  and  its  length.  The  case  of  the  paraffin 
series  is  given  as  example. 

9.  In  the  more  general  and  more  interesting  DYNAMICAL 
METHOD,  the  rotary  motion  of  atoms  around  their  longer  axis 
is  made  use  of;  it  is,  of  course,  applicable  to  liquids  only.  In 
this  case  the  atom -volume  is  a cylinder  of  revolution,  the  base 
of  which  is  the  circle  described  in  the  rotation,  while  the  length 
is  that  of  the  axis  itself. 

10.  This  method  has  been  applied  to  OVER  SIXTY  ETHERS 
for  which  the  necessary  data  are  known.  The  results  of  the 
calculations  agree  admirably  with  the  observations.  The 
cross  section  of  these  ethers  is  one -third  larger  than  that  of 
the  paraffins.  This  is  the  expression  of  the  fact  that  the 
ethers  contain  the  link  O,  connecting  the  radicals,  projecting 


ATOMIC  VOLUME. 


m 


above  the  CH2  one-third  its  height.  See  C.  R.,  T.  113, 
p.  37;  1891. 

11.  One  of  the  most  remarkable  confirmations  of  this 
prismatic  or  cylindrical  form  of  the  atoms  of  serial  organic 
compounds  has  been  found  in  the  laws  of  the  MAGNETIC 
ROTATION  of  polorized  light  produced  in  liquids.  In  looking 
over  recent  work  of  W.  H.  PERKIN,  who  has  furnished  most 
elaborate  and  extensive  observations  in  this  field,  numerous 
further  confirmations  are  noticed.  C.  R.,  T.  113,  p.  500; 
1891. 


12.  The  exposition  of  this  subject  of  atomic  volume  in 
leading  MODERN  GERMAN  WORKS  is  really  astonishing. 
German  scientists  used  to  be  proud  to  know  work  done  in 
other  countries  as  well  as  that  done  within  the  limits  of  the 
old  Fatherland.  At  present,  this  has  become  merely  a historic 
reminiscence.  In  Ostwald’s  Biggest  Book  on  Chemistry,  the 
crude  ideas  of  Kopp  are  still  law,  and  the  search  for  the  fixed 
atomic  volume  of  each  element  atom  is  lustily  continued  as  it 
was  begun  fifty  years  ago. 


95.  ISOMERIC  ATOMS. 

1.  Having  established,  by  induction,  the  structure  of 
alcoholic  compounds,  we  may  now  make  use  of  the  easier 
METHOD  OF  DEDUCTION  to  establish  some  of  the  principal 
laws  governing  the  physical  properties  of  the  compounds. 

2.  The  first  compounds  which  invite  our  attention  are  the 
Isomerics  (84).  They  result  from  ISOMERIC  ATOMS,  namely 
different  structures  built  up  from  the  same  number  of  atoms 
of  the  same  elements,  in  accordance  with  the  laws  of  linkage. 

3.  Thus  the  paraffin  NORMAL  PENTANE  C5H12,  boils  at 
about  38  degrees.  It  is  normal,  having  its  five  links  all  in  one 
straight  line.  Chemical  treatment  has  failed  to  remove 
shorter  links  from  the  same.  It  has  no  lateral  branches. 


362 


LECTURE  95. 


4.  But  the  same  five  carbon  atoms  might  be  so  linked  as 
to  have  one  or  more  lateral  branches.  If  it  has  only  one  CH2 
lateral,  and  near  the  terminal,  it  is  called  ISO- PENTANE. 
This  hydrocarbon  boils  at  30  degrees,  fully  8 degrees  lower 
than  normal  pentane. 

5.  Finally  four  lateral  branches  CH3  might  be  bound  to 
one  central  carbon,  from  the  same  5 carbon  and  12  hydrogen 
atoms.  This  isomeric  compound  is  called  TETRA-METHYL 
METHANE.  It  boils  at  9.5,  about  30  degrees  below  the 
normal  pentane.  It  is  liquid  at  common  temperatures,  but 
fuses  at  —20. 

6.  Now  it  needs  only  a moment’s  consideration  to  under- 
stand these  REMARKABLE  DIFFERENCES.  As  the  carbons 
are  placed  in  the  lateral  branches,  their  distances  from  the 
center  become  less;  consequently,  the  moment  of  inerita, 
depending  on  the  square  of  these  distances,  must  greatly 
diminish.  Hence  the  boiling  point  must  be  lowered  corre- 
spondingly (92,  10  -12).  See  Plate,  page  78. 

7.  For  example,  the  MAXIMAL  MOMENT  OF  INERTIA 
(omiting  single  terminal  hydrogens)  of  normal  pentane  is 
10  CH2  = 140,  while  that  of  tetra- methyl  methane  is 
only  4 CH2  = 56,  or  about  one-third.  In  the  first  we  have 
two  links  CH2  at  the  distance  two,  giving  a moment  of  inertia 
4.  CH2  each.  In  the  final  isomeric,  these  two  links  are  at 
the  unit  of  distance,  and  only  give  the  moment  I.CH2  each. 
This  fully  explains  the  changes  in  boiling  points. 

8.  As  links  are  made  lateral,  the  MINIMAL  MOMENT  OF 
INERTIA  for  the  main  or  larger  axis  will  be  greatly  increased 
with  their  increased  distance  from  that  axis.  Accordingly, 
tetra- methyl  methane  melts  at  a temperature  at  which  normal 
paraffins  of  even  twice  that  number  of  carbon  atoms  remain 
liquid. 

9.  In  the  same  manner,  the  ISOMERIC  ALCOHOLS  con- 
taining 4 carbon  atoms  are  all  liquids  except  the  trimethyl 
carbinol,  having  three  lateral  arms  CH3.  It  forms  rhombic 
crystals  melting  at  28  degrees.  In  this  atom,  the  longer  axis  is 


ISOMERIC  ATOMS. 


3()3 


CH3-CH-OH  and  to  the  carbon  of  the  middle  the  two  CHg  are 
linked,  greatly  increasing  the  moment  of  inertia  for  this  axis. 

10.  MY  FIRST  PUBLICATION  on  this  subject  appears  in 
the  Proceedings  of  the  American  Association  for  the  Advance- 
ment of  Science  for  1868  (Chicago  meeting).  Complete 
mathematical  formulae  were  sent  in  my  Beitrage  to  the  Ger- 
man Chemical  Society  at  Berlin  in  1872,  of  which  1 was  a 
rnember.  Several  papers  of  mine  were  presented  by  Berthelot 
to  the  Academy  of  Sciences  of  Paris  and  published  in  the 
Comptes  Rendus  from  1873  on.  See  T.  113,  p.  798;  1891. 

11.  DR.  ALEXANDER  NAUMANN,  Professor  of  Chemistry 
at  the  University  of  Giessen,  Germany,  was  one  of  the 
paid  writers  for  the  Jahresbericht.  He  misrepresented  and 
condemned  my  paper  of  1868  on  this  subject  in  the  Jahres- 
bericht. In  1873  he  discovered  my  law  over  again  as  his  own, 
and  his  discovery  was  promptly  published  in  the  Berichte  of 
the  German  Chemical  Society  of  Berlin.  In  all  German 
chemical  publications  this  law  is  credited  to  Naumann,  even 
in  W.  Markwald’s  “Beziehungen”  which  were  crowned  with 
a prize  by  the  University  of  Berlin,  in  1888,  under  the  auspices 
of  Geheimrath  A.  W.  Hofmann. 

Thus  the  young  German  writers  on  the  Jahresbericht  make 
their  discoveries,  and  no  protest  is  raised  by  German  scien- 
tists. Until  that  is  done  they  must  be  considered  as  endorsers 
of  that  practice.  1 demanded  my  name  erased  from  the  list  of 
members  of  the  German  Chemical  Society  (March  27,  1874). 
See  my  Beitrage,  Leipzig,  1892. 

12.  It  will  readily  be  seen  that  the  structure  now  estab- 
lished fully  accounts  for  the  RIGHT-  AND  LEFT-HANDED 
(geometric)  ISOMERICS,  and  therefore  determines  the  charac- 
ter of  rotary  polarization.  A simple  construction  of  the 
stereographic  formulae  of  the  tartaric  acids  will  exemplify  this. 
Compare  figures  1,  2,  3,  page  394.  The  face-to-face  linkage 
of  carbon  is  most  essential  also  in  this  matter.  The  interest- 
ing hexachlorides  of  Benzol,  due  to  Friedel,  obtain  their  fullest 
importance  in  this  construction. 


96.  ATOMIC  ROTATIONS. 


1.  The  reality  of  ATOMIC  ROTATIONS  in  the  liquid  and 
gaseous  states  is  also  most  conclusively  demonstrated  by  the 
results  obtained  as  specific  heat  (39  and  40)  of  substances  in 
these  states.  We  shall  first  consider  the  specific  heat  of  gases. 

2.  The  specific  heat  of  a gramme-molecule  of  any  gas  or 
vapor  is  the  number  of  gramme -degrees  of  heat  required  to 
raise  the  temperature  thereof  one  degree  (centigrade).  If  the 
volume  be  kept  constant,  the  gas  does  no  external  work;  if 
the  PRESSURE  BE  KEPT  CONSTANT,  the  gas  expands  and 
thus  does  external  work.  According  to  G.  Schmidt,  this 
EXTERNAL  WORK  amounts  to  2 calories  (gramme  degrees). 

3.  While  the  temperature  changes,  the  particles  may  also 
act  upon  one  another,  and  thus  do  some  INTERNAL  WORK. 
For  perfect  gases,  like  oxygen  and  hydrogen,  this  amount  is 
not  measLireable,  but  for  vapors  it  may  be  of  appreciable  mag- 
nitude. We  will  represent  it  by  the  symbol  w. 

4.  THE  ACTUAL  ENERGY  OF  MOTION  is  represented  in 
the  vibration  of  the  atoms,  the  motion  of  translation  and  of 
rotation  of  the  entire  molecule.  The  first  depends  evidently 
upon  the  number  of  atoms  in  the  molecule.  Naumann  con- 
siders it  equal  to  as  many  calories  as  the  molecule  has  atoms; 
say  n.  The  motion  of  translation  represents  3 gramme 
degrees,  according  to  Clausius. 

5.  THE  MOTION  OF  ROTATION  requires  an  amount  of 
energy  proportional  to  the  moment  of  inertia,  1 of  the  mole- 
cule; hence  we  can  call  it  k I calories  per  gramme  molecule 
(Comptes  Rendus,  T.  76,  p.  1358;  1873,  and  Principles  of 
Chemistry,  1874;  p.  118).  For  many  gaseous  alcoholic  com- 
pounds we  have  found  k one -eighth  of  a calory. 

6.  Thus  the  total  specific  heat  (under  constant  pressure) 
of  a gramme  molecule  of  any  GAS  OR  VAPOR  becomes 

S = 5-|-w  + n + kl 


ATOMIC  ROTATIONS. 


305 


For  LIQUIDS,  the  same  formula  will  obtain,  except  that  the 
external  work  is  insignificant  for  a degree,  and  that  the  moment 
of  inertia  i is  taken  for  the  longer  axis.  Hence 
S'  = 3 + w + n + ki 

7.  The  gases  and  vapors  considered  by  me  in  1873  agree 
excellently  with  this  formula  S and  therefore  PROVE  THE 
ROTATION  OF  THE  MOLECULES  of  gases  and  vapors  around 
that  permanent  axis  for  which  the  moment  of  inertia  is  a 
maximum.  We  shall  come  back  to  this  subject  in  the  next 
lecture. 

8.  THE  ETHERS  OF  THE  FATTY  ACIDS  have  been  found 
to  be  truly  prismatic  bodies  (94,  10).  Their  moment  of  inertia 
is  accordingly  directly  proportional  to  their  length,  the  cross- 
section  being  the  same  throughout  each  one  and  for  all. 
Hence  the  specific  heat  per  unit  of  weight  must  be  the  same 
for  all  these  ethers  (C.  R.,  T.  113,  p.  469;  1891). 

9.  R.  SCHIFF  has  found  this  specific  heat  for  all  equal  to 
0.442;  he  has  studied  27  of  these  ethers  (1.  c.)  Ostwald 
declared  this  result  to  be  “most  unexpected.”  But  we  see 
that  it  is  simply  the  expression  of  the  equal  cross-section  of 
all  these  prismatic  bodies.  THE  DETERMINATION  OF  SCHIFF 
therefore  are  a direct  demonstration  of  the  rotation  of  the 
molecules  of  these  liquids  around  their  longer  axis. 

10.  FOR  SOLIDS,  the  term  containing  the  moment  of 
inertia  disappears,  because  the  molecules  of  solids  do  not 
rotate.  The  expression  in  6 is  reduced  to 

S'  = 3 + w + n 

where  the  internal  work  w now  becomes  very  considerable. 
These  results,  being  old  and  long  established,  need  not  be 
considered  here. 

11.  The  specific  heat  of  the  SOLID  ELEMENTS  are  equal, 
namely  nearly  6 ; hence  the  internal  work  is  about  3.  Ber- 
thelot  has  first  (1873)  pointed  out  that  elements  herein  radi- 
cally differ  from  all  compound  matter.  1 have  shown  (1892; 


366 


LECTURE  97. 


C.  R.,  July  25)  this  to  be  due  to  the  fact  that  the  element- 
atoms  oscillate  as  a unit,  or  that  THEIR  COMPONENT  PARTS 
ARE  INVARIABLY  FIXED,  not  mutually  movable. 

12.  Recently  Berthelot  (C.  R.  Jan.  18,  1897)  has  care- 
fully compared  the  specific  heat  of  the  elementary  gases  and 
of  ARGON  AND  HELIUM.  He  thinks  it  probable  that  they 
vary  as  1 : 2 : 4 according  as  the  molecule  contains  1,  2,  4 
atoms.  But  he  has  overlooked  the  atomic  rotations. 

The  entire  difference  between  6,8  (chlorine)  and  4,8 
(oxygen)  corresponds  to  AN  INCREASE  OF  ONLY  16  PER 
CENT.  IN  THE  DISTANCE  between  the  two  atoms  of  chlorine 
in  its  molecule  over  that  of  the  oxygen  atoms.  The  latter 
does  not  dissociate,  the  former  does  yield  to  heat. 


97.  ATOMIC  LIBRATION. 

1.  When  Galileo  had  directed  his  telescope  upon  the  face 
of  the  moon,  he  recognized  slight  changes.  It  seemed  that  the 
moon’s  face  turned  a little,  like  the  beam  of  a balance.  He 
accordingly  called  the  phenomenon  the  LIBRATION  OF  THE 
MOON.  It  has  occupied  observers  and  mathematicians  for 
over  a century. 

2.  The  real  home  of  the  balance  is  the  chemical  laboratory. 
THE  TRUE  LIBRATION  IS  THAT  OF  THE  ATOMS.  It  is  of 
more  decided  importance  in  molecular  mechanics  than  that  of 
the  moon  in  cosmical  mechanics.  It  is  of  infinitely  greater 
extent,  also.  Such  ‘’titubazione”  in  macrocosmos  would  be 
destruction. 

3.  Are  the  PHENOMENA  OF  ATOMIC  LIBRATION  occult 
and  hard  to  see.?  Oh,  no!  They  are  so  manifest  that  they 
stand  boldly  out  from  the  tabulated  data  of  boiling  points,  of 
fusing  points,  circular  polarization,  magnetic  rotation,  and 
others. 


ATOMIC  LIBRATION. 


3C7 


4.  What  phenomena  are  here  referred  to  as  due  to  atomic 
librations?  The  whole  world  of  TAR-DERIVATIVES  is 
dripping  full  of  them!  There  is  benzol,  crystallizing  at  about 
the  same  temperature  as  does  water.  Put  one  chlorine  in  the 
place  of  one  of  its  hydrogen,  and  down  goes  the  fusing  point 
half-a-hundred  degrees.  Replace  still  another  atom,  and  the 
fusing  points  jumps  up  a hundred  degrees.  Thus  it  keeps 
alternating  up  and  down,  while  the  benzol  atom  is  being 
gradually  loaded  with  chlorine  instead  of  with  hydrogen. 
Here  you  have  the  continuity  of  nature  in  the  chemical  pro- 
cess, and  rank  discontinuity  in  the  physical  result.  The 
chemist  moves  by  continuous  steps — and  nature  jumps  like  a 
see -saw! 

5.  And  in  truth,  IT  IS  A SEE-SAW.  You  balance  a plank 
nicely.  A little  boy  jumps  on — down  goes  his  end  of  the 
plank.  The  boy’s  playmate  manages  to  get  onto  the  plank 
and  walks  to  the  other  end— down  that  goes,  carrying  up  the 
first  one.  Here  we  have  the  libration  of  a plank,  produced  by 
two  little  imps  full  of  fun  and  mischief.  Atomic  libration  is 
mechanically  produced  in  the  same  manner. 

6.  Here  is  a benzol  atom  (Plate  page  395) ; THE  FAMOUS 
BENZOL  RING  AS  IT  IS  IN  REALITY,  shown  in  ground  plan 
or  horizontal  projection,  in  accordance  with  our  established 
atom -linkage.  Suppose  the  hydrogen  atom  place  1 be 
exchanged  against  an  atom  of  bromine.  What  will  happen? 

7.  The  total  benzol  weighs  78.  The  single  bromine  sub- 
stitution adds  79  thereto  and  doubles  it.  The  CENTER  OF 
GRAVITY  moves  from  the  center  of  the  ring  half  way  towards 
place  1.  The  effect  on  the  moment  of  inertia  for  the  vertical 
axis  is  easily  calculated — determining  the  boiling  point.  For 
the  axis  parallel  to  the  paper,  determining  the  fusing  point, 
the  case  is  a little  more  complicated. 

8.  The  old  axis — for  benzol  itself — was  parallel  to  the  plane 
of  the  projection,  and  passed  through  the  center  of  the  ring, 
that  being  the  center  of  gravity.  THE  NEW  AXIS,  for  the 


368 


LECTURE  97. 


mono-bromide,  FORMS  QUITE  AN  ANGLE  with  that  plane, 
roughly  passing  through  the  bromine  atom  and  that  center  of 
the  ring.  Thus  the  added  weight  of  bromine  at  distance  zero 
adds  almost  nothing  to  the  moment  of  inertia,  which  has  been 
greatly  reduced  by  the  displacement  of  the  center  of  gravity. 

9.  But  now  add  another  atom  of  bromine  where  it  will 
produce  THE  GREATEST  MECHANICAL  EFFECT,  that  is  IN 
PARA- POSITION,  at  4.  Since  the  H or  Br  at  1 is  in  the  plane 
of  carbons,  2,  4,  6 and  the  H or  Br  at  4 in  plane  with  carbons 
1,  3,  5,  the  two  bromine  in  para-position  (1,  4)  balance, 
restore  the  center  of  gravity  to  the  center  of  the  ring.  Hence 
we  have  their  full  distance  effected  in  the  moment  of  inertia, 
which  goes  up  about  twice  as  much  as  the  first  depressed  it. 
In  the  tetra-bromide  (1,  4;  2,  5)  we  have  two  para-positions ; 
hence  double  rise  of  melting  point.  In  hexa  bromide  we  have 
three  para-positions  (1,  4;  2,  5;  3,  6)  and  hence  threefold 
rise.  The  change  of  inclination  becomes  less  as  the  total 
weight  increases.  Hence  the  rise  in  fusing  point  for  the 
second  and  third  para — addition  is  greater  than  for  the  first. 

In  the  tri- bromide  (1,  4;  2)  we  have  the  para  position 
(1,  4)  added  to  2.  So  also  the  penta-bromide  is  one  added  to 
the  di-para  (1,  4;  2,  5).  The'  diagram  for  chlorides  shows 
from  Benzol  the  fusing  points  of  the  para-compounds  at 
B,  D,  F (mono-,  di-,  tri-para)  and  the  depressed  monochlorid 
at  A,  raised  by  two  paras  (mono-,  di-)toCandE.  Page  395. 

This  is  the  simplest  case  of  atomic  libration.  Without 
using  a mathematical  formula  I trust  THE  PROBLEM  IS 
CLEARLY  STATED  AND  ITS  SOLUTION  FULLY  INDICATED. 
The  plate  (p.  395)  shows  that  the  case  is  general,  applying 
to  all  chloroids.  For  radicals,  the  case  will  be  modified  by  their 
open  structure,  as  shown  long  ago.  See  C.  R.,  T.  115, 
p.  177;  1892. 

10.  It  will  be  understood  that  these  LIBRATIONS  AFFECT 
NEARLY  ALL  PROPERTIES.  Thus  the  para-compound  neces- 
sarily occupies  the  greatest  volume — as  Feitler  has  found 
experimentally.  Our  modern  journals  are  full  of  facts — for  it 


ATOMIC  LIBRATION. 


3G9 


is  facts,  you  know,  new  observations,  “eigene  Bestim- 
mungen,”  that  our  Geheimrathe  want — for  such  things  can 
be  manufactured  by  the  students,  and  be  published  “in 
stattlichen  Banden.” 

11.  The  state  of  my  health  has  not  allowed  me  thus  far  to 
publish  either  of  the  volumes  planned  to  succeed  my  True 
Atomic  Weights.  The  solution  here  given  is,  however,  broad 
and  complete.  ANYONE  UNDERSTANDING  MECHANICS 
CAN  PUT  THE  SOLUTION  INTO  EQUATIONS.  It  is  a simple 
matter  of  detail.  I will  only  add,  that  the  case  of  “odd  and 
even  compounds”  of  alcoholics  (Lect.  93)  is  really  also  involv- 
ing an  inclination  of  the  axis,  especially  where  the  terminal  is 
heavy,  and  the  number  of  carbons  low,  as  in  formic  and  acetic 
acids.  One  of  the  most  interesting  cases  of  atomic  libration 
is  presented  in  the  THREE  CHLORACETIC  ACIDS;  however, 
the  calculations  are  rather  intricate. 

12.  The  Ring- Form  of  Benzol  has  been  demonstrated  by 
my  formulae  in  1874  (Principles,  p.  120;  also  C.  R.,  T.  80, 
p.  47;  1875).  The  above  formula  (Lect.  96,  6)  for  benzol 
vapors  gives  I — 70,  since  S 29.26  observed,  and  n = 12,  the 
internal  work  being  taken  at  3.5  as  for  alcoholics.  If  this  be 
less,  the  moment  I will  be  correspondingly  greater. 

But  for  the  six  CH  forming  a straight  line,  the  moment 
would  be  at  least  227.  This  is  entirely  at  variance  with  the 
above  value  due  to  the  specific  heat.  If  the  center  of  gravity 
of  the  six  carbons  be  at  a distance  r and  those  of  hydrogen 
at  r,  the  moment  of  inertia  will  be  6.  [C.r^  + H.r,^] . 
Taking,  as  first  approximation  r,  = r we  find  r = 0.95.  This 
is  very  nearly  the  value  1.00  of  our  construction,  p.  395. 


Note. — In  looking  through  Perkin’s  determinations  of  magnet  rota- 
tions in  the  closing  number  for  1896  of  the  bulky  Zeitschrift,  I notice  a 
multitude  -of  the  plainest  confirmations  of  these  principles.  The  o 
much  greater  than  p (p.  633)  because  ortho  have  new  weights  nearest 
and  on  opposite  sides  of  the  central  plane — producing  maximal  torsion. 
So  a naphtols  greater  than  ft,  p.  635. 


98.  ATOMIC  CRYSTALS. 


1.  The  old  Teutons  and  Scandinavians  believed  that 
“Cobolde”  and  “Nisser”  inhabit  the  caves  of  the  earth, 
gather  metals  and  skillfully  work  them  into  ornaments  and 
weapons  which  they  bestow  as  gifts  on  their  favorite  among 
women  and  men.  But  if  man  surprises  them,  these  dwarfs 
suddenly  assume  the  form  of  beautiful  crystals,  which  there- 
fore are  called  QUARTZ  (dwarf).  See  Dedication,  3rd  section. 

2.  The  magnificient  quartzes  of  the  Alps  were  well  known 
to  the  Romans,  for  Pliny  speaks  of  them  at  length  (15,  2). 
They  supposed  them  to  arise  from  celestial  vapors  and  purest 
snow;  but  WHY  THEY  GROW  SIX-SIDED,  Pliny  deems  it 
hard  to  tell.  Quare  sexangulis  nascitur  lateribus  non-facile 
ratio  inveniri  potest  (Hist.  Nat.  37,  9). 

3.  From  celestial  vapors  forms  purest  snow  indeed — and 
that  SNOW  HAS  ALSO  THE  SIX-SIDED  FORM.  Every-one  in 
northern  countries  can  see  these  star-like  forms  if  he  will  but 
look  at  the  snow  lodging  on  his  coat  on  a dry,  cool  winter  day 
while  snow  is  falling.  A simple  magnifier  will  reveal  most  of 
the  beauties  of  these  snow -stars. 

4.  Though  so  common  and  abundant  an  object,  the  real 
six-sided  form  of  the  snow -star  was  not  noticed  before  Kepler, 
who  described  them  1611  in  a special  publication  of  24  pages 
quarto : DE  NIVE  SEXANGULA.  How  did  it  happen  that  the 
astronomer  Kepler  saw  what  all  others  had  overlooked.? 

5.  Kepler’s  mind  was  filled  with  the  PYTHAGOREAN  AND 
PLATONIC  IDEAS  of  geometrical  and  numerical  harmonies  in 
Nature.  He  had  published  (1596)  his  Mysterium  Cosmo- 
graphicum,  in  which  the  five  regular  bodies  are  made  to 
determine  the  dimensions  of  the  planetary  system.  In  1619 
he  finally  completed  his  search  for  the  great  laws  of  the  solar 
world,  as  published  in  his  Harmonices  Mundi. 


ATOMIC  CRYSTALS. 


371 


6.  No  wonder  that  such  a man  would  notice  with  delight 
the  beautiful  and  regular  forms  of  the  six-sided  snow-stars! 
He  even  went  further  and  asked:  Cur  antem  sexangula.? 
This  question  has  remained  until  1 showed  in  my  Programme 
(1867)  WHY  THE  SNOW-STAR  IS  SIX-SIDED.  In  the  Scien- 
tific. American  for  April  18,  1868,  this  question  is  fully 
answered  in  popular  form. 

7.  Water  is  represented  by  the  formula  Ha  O.  Every 
atom  of  water  consists  of  three  distinct  particles,  namely,  two 
of  hydrogen  and  one  of  oxygen.  But  three  equal  material 
points  can  only  remain  in  stable  equilibrium  if  they  are  equi- 
distant, that  is,  FORM  AN  EQUILATERAL  TRIANGLE.  These 
triangles,  aggregating  in  parallel  positions,  form  a regular  six- 
sided  star.  This  is  the  actual  form  of  the  snow- star.  See 
drawings  of  Glaisher  (below)  and  the  beautiful  microphoto- 
graphs (p.  53)  published  by  Dr.  Hellmann  (Berlin,  1893). 


; 

1 V \ / 1 — 1^ 

♦ 

■ ffe  ^ 

8.  The  formula  of  quartz  is  Si  O2.  Its  crystal  form  must, 
therefore,  also  be  hexagonal.  So  it  is.  Even  its  rotary 
polarization  is  accounted  for  in  this  way.  See  my  communi- 
cation UEBER  DEN  BAU  DES  QUARZES  to  the  Academy  of 
Sciences  of  Vienna,  presented  by  Haidinger  (Sitzungsberichte, 
I Abth.,  Bd.  61;  1870). 


372 


LECTURE  98. 


9.  This  explanation  must  be  supplemented  by  the  determi- 
nation of  THE  THIRD  DIMENSION  or  axis.  When  a liquid 
crystallizes,  its  molecules  cease  to  rotate;  they  aggregate 
according  to  the  quadratic  form  inscribed  in  the  cylinder  of 
rotation.  See  half  page  (3T)  from  my  Programme  der  Ato- 
mechanik  1867,  reproduced  on  page  399  in  two-thirds  its 
original  dimensions. 

10.  This  shows  the  cause  of  dimorphism  (21,  7).  At  the 
same  time,  the  constituent  atoms,  not  being  equal  in  the  com- 
pound or  crystal-atom,  the  exact  dimensions  will  be  subject 
to  small  pertubations  depending  on  the  actual  atomic  weights. 
These  MOLECULAR  PERTUBATIONS  have  been  determined 
in  my  paper  read  at  the  Salem  meeting  (1869)  before  the 
American  Association  for  the  Advancement  of  Science  (Pro- 
ceedings, pp. 100-112). 

11.  Even  the  case  of  TRIMORPHISM  of  titanic  oxide  has 
been  fully  considered  in  1867  (Programme  pp.  32-33).  It  may 
be  added,  that  Tridymite  is  the  ice-form  of  silica,  as  already 
published  in  a circular  of  August  1868.  A very  concise,  con- 
nected exposition  of  this  entire  subject  is  given  in  my 
PRINCIPLES  OF  PURE  CRYSTALLOGRAPHY,  1871;  44  pp. 

12.  THE  DETERMINATION  OF  THE  CRYSTAL-AXES 
from  the  measurement  of  the  crystal  angles  is  shown  in  the 
case  of  the  two  forms  of  sulphur  on  page  69.  It  is  evident 
that  the  inclination  Pq  gives  the  ratio  of  the  axes  B and  C, 
while  the  plane  angle  on  P gives  the  ratio  of  the  axes  A and  B 
in  native  sulphur  or  sulphur  crystallizing  from  its  solution  in 
bisulphide.  Lect.  21. 

13.  The  simple  case  of  sulphur  (p.  69)  also  shows  how 
THE  SECONDARY  FACES  P,  q,  are  related  to  the  primary 
octahedron  O,  the  dimensions  of  which  are  taken  as  the  axes 
A,  B,  C.  For  quartz  and  calcite,  a few  of  the  very  numerous 
secondary  faces  are  shown  on  plate  65.  The  plates  pp.  56  to 
64  give  reduced  copies  of  eighteen  of  the  excellent  plates  of  v. 
Kokscharow  showing  secondary  faces  of  leading  crystallized 


ATOMIC  CRYSTALS. 


373 


minerals.  These  plates  are  constantly  referred  to  in  crystal 
description  and  in  our  crystal  practicum. 

14.  The  true  ORIGIN  OF  SECONDARY  FACES  was  dis- 
covered by  the  crystalloclast,  Hauy  (see  p.  55).  A fine 
calcite  prism  (Fig.  1)  inadvertently  dropping  from  his  hands, 
he  found  that  its  cleavage  gradually  lead  to  the  fundamental 
rhombohedron  of  105  degrees,  see  Figures  2 to  5;  compare 
Lect.  11,  12.  From  the  scalenohedron  he  obtained  the  same 
cleavage  form  (Figures  G,  7).  So  he  did  from  all  other  calcite 
forms  (Fig.  8)..  Compare  calcite,  p.  65. 

15.  Accordingly,  Hauy  considered  a minute  cleavage 
rhombohedron  THE  CRYSTAL-MOLECULE  of  calcite.  By 
Figure  17  (p.  55)  he  shows  how  the  scalenohedron  is  built  up 
from  such  molecules.  On  page  392  we  copy  his  synthesis  of 
the  dodecahedron  and  the  pyritohedron  from  minute  cubes. 
In  a like  manner,  all  the  varied  tesseral  forms  (pages  58,  59) 
can  be  built  up  from  minute  cubes. 

16.  THE  MARKINGS  OF  THE  SURFACES  often  show  the 
reality  of  this  mode  of  growth  of  the  crystals.  The  striations 
of  the  cubes  of  pyrite  mark  the  lines  of  growth  of  the  pyrito- 
hedron (9,  12).  The  horizontal  stri^  of  the  prismatic  faces 
of  quartz  (Lect.  10,  6 and  plate  65)  mark  the  edge  z r,  and 
really  the  disc  of  Si  O2  atoms.  It  is  in  French  works 
that  nature’s  own  way,  recorded  by  Hauy,  is  still  properly 
presented.  See  Friedel,  Mineralogie,  Paris,  1893. 

17 . It  is  only  these  natural  forms  and  their  AXIAL  EQUIVA- 
LENTS OF  WEISS,  of  Berlin,  that  are  fit  for  use  in  the  study 
of  the  origin  of  crystal  forms  and  dimensions.  It  gives  me 
sincere  pleasure  to  see  that  the  author  of  the  best  crystallo- 
chemical  mannual.  Professor  C.  F.  Rammtlsberg  of  the  Uni- 
versity of  Berlin,  emphatically  expresses  the  same  views  and 
conforms  thereto  in  his  admirable  Handbuch  (First  edit.,  1855 
and  1857;  second,  1881,  1882). 

18.  This  mere  glance  at  the  origin  of  the  wondrous  crystal 
forms  may  suitably  be  closed  by  a reference  to  my  statistical 


374 


LECTURE  98. 


investigations  of  the  relative  FREQUENCE  OF  TFIE  FIIGFIER 
FORMS  OF  SYMMETRY,  presented  for  me  to  the  Academy  of 
Sciences  by  the  profound  Haidinger  (Sitzungsberichte,  Abth. 
1,  Bd.  62;  1870).  I find  the  higher  forms  of  symmetry 
excessively  predominant  in  nature.  The  probability  of  a 
tesseral  form  is  many  million  times  that  of  any  given  triclinic 
form. 

19.  A few  of  the  points  established  by  me  almost  thirty 
years  ago  and  published  in  the  Sitzungsberichte  of  the 
Academy  of  Sciences,  of  Vienna,  have  recently  found  their 
way  into  the  great  Leipzig  Organ  of  Ostwald— of  course  as  a 
new  discovery  (Retgers). 

20.  This  reminds  me  that  James  D.  Dana,  after  having 
studied  my  paper,  which  was  for  months  (1867)  in  his  poses- 
sion,  made  a complete  scientific  somersault  in  the  July  and 
September  numbers  of  his  Journal  for  1867.  Since  my 
Atomechanik  had  appeared  in  June,  he  was  compelled  to 
admit  priority  of  publication,  but  brazenly  claimed  “inde- 
pendent thought  in  independent  minds.”  It  is  remarkable 
that  the  mind  of  Dana  did  not  reach  the  third  dimension,  but 
only  my  law  of  symmetry  in  the  one  plane.  It  so  happened 
that  this  part  was  the  only  one  in  his  hands.  Flence  his  inde- 
pendent editorial  mind  could  not  proceed  for  lack  of  copy. 
Servility  bows  to  position  and  power;  but  honor  and  truth  will 
prevail  in  the  end. 


SUPPLEMENT  TO  ATLAS. 

But  few  of  the  instruments  intended  to  be  shown  were  left  in  each 
group,  which  still  shows  some  overlapping  and  thus  may  call  for  verbal 
explanation.  Space  demands  limitation  to  the  most  remarkable  case, 
the  compound  blowpipe  on  page  38S.  The  Kipp  produces  the  oxygen 
(p.  170).  This  is  probably  the  simplest  possible  manner  of  showing  the 
Tuagnificient  shower  of  sparks  from  burning  watch  springs  and  the 
dropping  of  molten  platinum  from  a good  sized  wire.  Instead  of  illumi- 
nating gas  here  used,  another  Kipp  will  furnish  the  hydrogen  gas,  and 
complete  the  outfit.  The  compound  jet  must  have  fine  perforations  and 
be  nicely  adjustable.  I use  a jet  taken  from  a calcium  light  outfit  for 
compound  gases. 


99.  ATOMIC  WEIGHT. 


1.  The  smallest  particle  of  matter  entering  into  chemical 
combination  with  any  other  such  particle,  is  called  a CHEMI- 
CAL ATOM.  Its  weight  is  called  the  atomic  weight  of  the 
substance  concerned,  expressed  in  any  convenient  unit  of 
weight.  The  methods  used  and  results  obtained  in  the 
determination  of  the  atomic  weights  of  the  elements  have 
been  given  (Lect.  40). 

2.  Dalton  introduced  this  idea  into  chemistry,  about  a 
century  ago  (Lect.  40,  Note).  His  TABLE  OF  ATOMIC 
WEIGHTS  was  small,  but  remarkably  good  for  a first  attempt. 
Both  his  law  of  combination  and  the  real  values  of  the  atomic 
weights  received  their  experimental  demonstration  at  the 
hands  of  that  great  chemist  who  for  a life  time  was  without 
a peer — Berzelius,  of  Sweden  (p.  22). 

3.  BERZELIUS  devised  the  most  exact  methods  of  analysis 
and  applied  these  methods  during  forty  years  to  the  determi- 
nation of  the  atomic  weights  of  the  elements,  several  of  which 
he  himself  discovered  (Se,  Si,  Th,  Va).  The  first  connected 
exposition  of  his  results  are  given  in  his  Essay  sur  la  theorie 
des  proportions  chimiques,  Paris,  1819.  This  work  also  forms 
part  of  his  elements  of  chemistry,  which  for  a quarter  of  a 
century  remained  the  textbook  of  the  chemical  world. 

4.  In  1840,  DUMAS  (p.  25)  began  his  fundamental  work 
on  atomic  weights,  determining  that  of  carbon  and  of  hydro- 
gen in  reference  to  oxygen  (Lect.  31,  3 — 8).  The  atomic 
weight  of  oxygen  being  taken  at  16,  that  of  hydrogen  is  1, 
that  of  carbon  (diamond)  is  12,  exactly.  His  work  has  unjustly 
been  drawn  in  question.  He  also  made  admirable  determi- 
nations on  silver  in  the  dry  way  (21,  10). 

5.  STAS  (p.  33)  was  permitted  to  assist  Dumas  in  his 
combustion  of  the  diamond.  He  made  many  determinations 
at  Brussels,  on  silver  and  its  nitrate,  sulphate  and  sulphide, 
and  especially  in  the  wet  way  with  chlorine,  bromine  and 


370 


LECTURE  09. 


iodine.  He  knew  to  .surround  his  results  with  a halo  of 
excessive  accuracy  in  the  form  of  mathematical  calculations; 
but  since  his  atomic  weights  vary  with  the  amount  operated 
upon,  the  accuracy  assumed  is  nol  real. 

6.  Since  Hofmann  of  Berlin  made  chemical  patents  so 
popular  among  German  chemists,  the  latter  have  added 
scarcely  anything  to  this  field  of  science,  beyond  the  most 
extravagant  endorsement  of  the  perfection  and  accuracy  of  the 
results  of  Stas.  To  question  the  absolute  reliability  of  the 
values  of  Stas— and  of  his  philosophical  conclusions — is 
generally  taken  in  the  Fatherland  as  a sign  of  inferioity. 

7.  As  a glaring  specimen,  I have  printed  a complete  trans- 
lation of  the  ENDORSEMENT  OF  STAS  by  the  editor  of  the 
Jahresbericht  and  his  thirteen  paid  aids.  See  my  True 
Atomic  Weights,  p.  37 — 38;  1894.  The  absurdity  of  the 
style  and  language  of  this  document,  and  the  evident  lack  of 
understanding  of  the  subject,  makes  it  one  of  the  most  charac- 
teristic documents  of  modern  chemistry. 

8.  STAS  AND  HIS  SCHOOL  BELIEVE  they  have  demon- 
strated that  THE  ATOMIC  WEIGHTS  OF  THE  ELEMENTS 
ARE  NOT  EXACT  MULTIPLES  of  half  the  atomic  weight  of 
hydrogen.  Stas  and  his  school  therefore  consider  it  experi- 
mentally demonstrated  that  the  chemical  elements  cannot  be 
taken  as  compounds  of  one  single  material  or  substance. 

9.  In  the  work  of  mine  just  referred  to  (256  pp.  with  many 
plates)  I have  critically  examined  both  the  chemical  work  and 
the  mathematical  reductions  thereof.  My  result  has  been 
that  BOTH  THE  CHEMICAL  WORK  AND  THE  MATHE- 
MATICAL REDUCTIONS  THEREOF  are  entirely  unworthy  of 
the  consideration  in  which  they  are  held,  a consideration  due 
to  lack  of  real  critical  study. 

10.  The  chemical  work  of  Stas  does  not  comply  with  the 
first  condition  of  all  chemical  analysis,  that  its  results  must  be 
independent  of  the  amount  operated  upon.  IT  IS  ABSURD  to 
suppose  that  the  atomic  weight  of  silver  can  vary  according 
as  it  is  part  of  10  grammes,  100  grammes  or  400  grammes. 


ATOMIC  WEIGHT. 


377 


The  Stasians  say,  these  differences  are  small ; true,  but  they 
are  of  the  very  magnitude  on  which  the  conclusion  they  draw 
depends  for  support.  See  plate,  page  79. 

11.  THE  MATHEMATICAL  REDUCTIONS  of  the  Stasian 
school  (made  by  Ostwald,  Karl  Seubert,  Lothar  Meyer  of 
Germany,  Thomsen  of  Denmark,  Sebelien  of  Norway,  Van 
der  Plaats  of  Holland,  F.  W.  Clarke  of  the  United  States)  is 
something  really  astonishing.  It  would  be  decidedly  amusing, 
if  the  errors  which  this  school  supports  by  its  spurious  science 
were  not  so  serious  in  their  consequences. 

12.  I do  not  need  to  enter  upon  details  in  this  place.  I 
may  refer  to  my  book,  THE  TRUE  ATOMIC  WEIGHTS  of  the 
Chemical  Elements  and  the  Unity  of  Matter,  St.  Louis,  Mo., 
U.  S.,  1894.  The  main  topics  of  this  work  were  first 
published  in  the  Comptes  Rendus  of  the  Academy  of  Sciences 
of  Paris,  in  volumes  115  to  118  (1892 — 1894),  thanks  to  the 
kindness  of  Berthelot. 

13.  Not  only  the  entire  method  of  reduction  used  at 
present  is  faulty,  but  our  chemists  employ  a sort  of  FLOAT- 
ING BUOY  INSTEAD  OF  FIXED,  IMMOVABLE  MARK.  It  is 
incredible,  but  true.  Hence  they  never  can  tell  where  they 
are.  See  Comptes  Rendus,  T.  116,  p.  695;  1893.  The 
proper  method  to  be  used  is  also  presented  in  that  article. 

14.  Furthermore,  it  is  necessary  to  adopt  the  most  perma- 
nent and  definite  element  as  the  STANDARD  OF  MATTER  for 
the  system  of  atomic  weights.  THE  DIAMOND  is  the  only 
elementary  substance  that  can  be  used.  For  details  see 
Comptes  Rendus,  T.  117,  p.  1075;  1893.  Also  True  Atomic 
Weights,  p.  174.  The  system  of  weights  so  resulting  is 
represented  on  page  398. 

15.  Publications  of  the  Smithsonian  Institution  and  the 
position  of  our  government  chemists  are  strongly  Stasian.  So 
is  the  work  of  the  young  chemist  at  Harvard  and  that  of 
Professor  Morley,  whose  work  for  years  has  been  assisted  by 
funds  of  the  American  Association . for  the  Advancement  of 
Science.  They  ought  to  be  satisfied  with  the  overwhelming 


378 


LECTURE  99. 


majority  and  not  suppress  an  individual  dissenter.  It  is  just 
barely  possible  that  nature  alone  decides. 

16.  While  our  Stasian’s  rejoice  in  the  results  of  Morley 
and  applaud  his  presidential  address  at  Buffalo  (August,  1896), 
we  hear  from  Leduc  of  Paris  (C.  R.,  T.  123,  p.  807;  1896) 
that  the  weight,  in  grammes,  of  a litre  of  oxygen  is  1.4293, 
of  nitrogen  1.2507.  Now  one-sixteenth  of  the  first  is 
0.08933  and  one-fourteenth  of  the  latter  is  0.089335.  THESE 
ATOMIC  WEIGHTS  ARE  CERTAINLY  COMMENSURABLE. 

17.  The  value  of  this  quotient  should  agree  with  the 
weight  of  a liter  of  hydrogen  gas,  see  page  196.  THE 
WEIGHINGS  OF  HYDROGEN  made  are  0.0898  or  about  half 
a milligramme  in  excess  per  liter.  Of  course,  our  experi- 
menters, especially  Professor  Morley,  could  not  commit  such 
an  error.  His  hydrogen,  he  says,  was  pure.  And  yet,  it  is  a 
fact,  that  for  a century  our  experimenters  overlooked  THAT 
LITTLE  ONE  PER  CENT.  OF  ARGON  in  the  air,  and  relied  on 
the  false  weight  of  nitrogen  until  Lord  Rayleigh  discovered 
this  source  of  error! 

18.  I cannot  close  this  lecture  without  mentioning  two  of 
our  younger  American  chemists  working  in  this  line — Professor 
RICHARDS  at  Harvard,  and  Professor  EDGAR  F.  SMITH  at 
Philadelphia.  The  former — a dyed  in  the  wool  Stasian — 
recently  found  Mg  24.5,  by  starting  with  something  he  does 
not  know  what,  and  ending  with  something  he  knows  as  well. 
This  result  represents  an  error  of  over  two  per  hundred  on  the 
value  Mg  24.  I am  not  competing  in  this  work;  but  my 
gasometric  work  proves  that  the  fine  work  done  at  Harvard  is 
altogether  too  fine.  A little  error  of  two  per  cent,  in  the 
atomic  weight  of  an  element  used  in  many  quantitative 
determinations  (phosphate,  etc.)  is  really  a tangible  and 
substantial  achievement  for  Old  Harvard. 

In  the  Laboratory  of  the  University  of  Pennsylvania,  atomic 
weight  determinations  are  also  made.  1 have  been  delighted 
with  the  evidence  that  Professor  Smith  deems  is  as  necessary 
to  weigh  known  substances  as  BERZELIUS  did. 


100.  ALCHEMY  AND  ELEMENT. 


1.  The  researches  of  Berthelot  in  THE  EARLY  HISTORY 
OF  CHEMISTRY  are  as  important  as  they  have  been  extended 
(see  pages  42,  43).  An  outline  of  his  labors  we  have 
in  the  elegant  edition  (Paris,  1885)  of  his  fascinating  work: 
Les  Origines  de  I’Alchimie.  His  later  works  have  been  on  a 
large  scale  every  way. 

2.  Berthelot  has  strongly  accentuated  the  kinship  of 
thought  between  the  alchemist  and  the  modern  chemist  in 
reference  to  THE  CONSTITUTION  OF  MATTER.  What 
sounded  strange  forty  years  ago  to  prominent  men  in  letters 
of  mine,  and  thirty  years  ago  in  my  Programme  (1867)  is 
now  tacitly  admitted. 

3.  Says  Professor  Schiitzenberger  in  his  introduction  to 
the  lecture  on  my  True  Atomic  Weight:  “To  him  (i.  e. 
Hinrichs),  and  we  may  say,  somewhat  to  all  of  us,  the 
elements  of  which  the  material  world  is  composed,  are  the 
result  of  the  condensation,  according  to  certain  laws,  of  a 
single  principle,  which  he  (Hinrichs)  calls  PANTOGEN.” 
Actualites,  p.  4;  1896.  See  dedication,  last  clause. 

4.  This  is  not  the  place  nor  the  time  for  a historic  expo- 
sition of  ATOM  MECHANICS;  but  we  may  state,  that  by 
publications  and  by  letters  received  we  could  easily  show  that 
this  change  has  been  mainly  due  to  our  own  work,  a notable 
part  of  which  is  still  credited  to  those  who  merely  appropriated 
it  surreptitiously,  as  did  Naumann,  Dana,  Lothar  Meyer  and 
a few  others. 

5.  This  implies  that  many  of  the  Stasians  do  not  believe 
in  their  own  statements.  It  is  palpably  impossible  to  admit 
the  Stasian  Atomic  Weights  and  at  at  the  same  time  conceive 
the  elements  to  be  compounds  of  some  primitive  matter  or 
perhaps  a few  such  materials  (if  that  were  not  almost  equally 
self-contradictory) . 


380 


LECTURE  100. 


6.  Now,  we  have  shown  the  Stasian  Atomic  Weights  to  be 
erroneous  to  a much  greater  extent  than  necessary  to  destroy 
their  value  as  an  argument  for  the  complexity  of  the  elements. 
We  have  found  all  well  established  atomic  weights  multiples 
of  one  twenty-fourth  of  that  of  carbon,  correspondingly  to  half 
the  atomic  weight  of  hydrogen.  True  Atomic  Weights, 
p.  208—213. 

7.  As  to  constitution,  the  elements  may  be  divided  into 
three  systems,  namely  THE  HYDROGEN,  CARBON  AND 
IRON  SYSTEMS.  The  last  two  are  very  comprehensive. 
They  vary  in  two  ways,  in  valence  and  in  weight.  We  shall 
consider  each  of  these  variations  separately. 

8.  Let  us  start  with  the  monad  carbon,  C = 12;  and  see 
how  it  varies  in  weight.  First  by  simple  increase  in  length, 
the  weight  a and  2a  added  gives  a heavy  and  a light  dyad. 
See  plate,  page  80.  Here  a is  16.  Hence  the  heavy  dyad 
is  Si  28  and  the  light  dyad  — ? 44.  These  combinations  corre- 
spond to  binary  compounds  of  elements. 

9.  Either  of  these  dyads  next  combines  with  three,  and  six 
and  twice  six  a,  like  ternaries  (nitrates,  chlorates)  but  under 
more  or  less  previous  surrender  of  weight  to  secure  complete 
combination — as  H has  to  be  surrendered  to  make  hydrocar- 
bons combine.  In  the  carbon  group  we  have  instead  of 
3 A = 48  and  6 a = 96,  only  45  and  89,  leaving  3 and  7 for 
the  tie  holding  the  a together  around  the  dyads. 

10.  THE  CHANGE  IN  VALENCE  is  combined  with  a change 
in  electrical  character.  Carbon  has  the  valence  4 and  is 
about  equally  positive  and  negative.  Increase  of  matter 
makes  it  negative  and  decrease  makes  it  positive.  Thus: 
12  4-  2 = 14  = N,  12  -f  4 :=  16  = O and  12  -h  7 = 19  = FI 
are  increasingly  negative  and  of  valence  3,  2,  1 respectively. 
So  12  — 1 = 11  = Bo,  and  substraction  of  2 more  gives  suc- 
cessively 9 = Be  and  7 = Li,  the  positive  elements  of 
valence  3,  2,  1. 

11.  Between  the  positive  and  negative  valence  One  we 
have  long  suspected  a VALENCE  ZERO;  our  general  formula  of 


ALCHEMY  AND  ELEMENT. 


381 


1874  (Principles,  page  180,  181)  and  comparison  to  hydro- 
carbons paralleled,  shows  this.  This  group  of  elements  evi- 
dently is  represented  by  argon  and  helium.  For  a = 2 (10  — n) 
gives  for  the  valence  n = o,  a = 20.  We  will  not  now 
further  enlarge  on  the  production  of  positive  and  negative 
electric  character  by  removal  and  addition  of  matter  to  the 
carbon.  See  diagram  at  upper  right  hand  of  Plate  80. 

12.  The  iron  system  corresponds  exactly  hereto,  except 
that  ITS  ELECTRICAL  CHARACTER  IS  REVERSED,  that  is, 
becomes  negative  by  substraction  of  matter.  This  is  already 
strongly  marked  in  my  Programme  (1867)  in  the  reversal  of 
the  spiral,  § 37,  p.  9 (see  Plate  396)  specified  in  § 54,  p.  10. 

13.  The  diagram,  Plate  397,  gives  an  ideally  complete 
view  of  THE  COMPOSITION  OF  THE  ELEMENTS.  The  car- 
bon system  (C  12,  smaller  disks)  starts  near  the  center 
(pantogen)  and  divides  into  light  (open)  and  heavy  (full 
disks).  The  iron  system  starts  farther  from  the  center 
(Fe  = 56,  larger  disks).  The  Argonoids  and  Adamantoids  are 
opposite  extremes,  joined  by  the  1,  2,  3 atomic  negatives  and 
positives  in  upper  and  lower  half  of  diagram. 

14.  There  is  of  course  no  such  a thing  as  a real  PERIODIC 
SYSTEM  of  the  elements — consecutive  spires  of  eight  elements 
each,  increasing  the  atomic  weight  by  sixteen  for  each  spire. 
This  is  nothing  but  a hasty  generalization  from  my  Atome- 
chanik  of  1867  on  the  part  of  Lothar  Meyer.  He  reviewed  my 
book,  condemned  it;  then  published  his  periodic  law.  See 
how  MendelejefPs  is  only  a reflection  of  mine,  top  figure,  page 
398  where  A-B  represents  a vertical,  plane  mirror.  Details^ 
True  Atomic  Weights,  pp.,  227-255. 

15.  All  about  the  valencies  is  given  in  my  Programme 
(1867,  p.  11-17),  where  also  diagram  of  valencies  is  given  on 
page  15,  here  reprinted,  page  385.  The  wall  chart  (p.  391) 
has  hung  for  twenty  years  in  my  lecture  hall  in  Darkest 
America;  it  is  the  above  (plate  396)  more  carefully  drawn. 
Adapted  to  letter  press,  we  used  diagrams  p.  73.  Look  at  that 
in  a mirror,  you  have  the  so-called  Mendelejef’s,  see  p.  398» 


382 


LECTURE  100. 


16.  The  constititution  here  given  makes  it  most  probable, 
that  when  intensely  heated  in  a properly  resistent  autoclave, 
DOUBLE  DECOMPOSITIONS  OF  THE  ELEMENTS  may  be 
produced  (True  Atomic  Weights,  p.  224). 

Most  assuredly,  THE  CENTRAL  PARTS  OF  THE  EARTH 
consist  mainly  of  the  heaviest  metals  (Au,  Pt).  The  specific 
gravity  of  the  nucleus  must  be  at  least  16  (Plana);  hence 
must  consist  mainly  of  these  and  kindred  metals.  The  physi- 
cal and  chemical  properties  of  the  elements  are  functions  of 
the  form  and  weight  of  their  atoms. 

17.  At  the  close  of  this  hasty  glance  at  the  chemical 
composition  of  the  elements,  we  thus  come  to  ADOPT  THE 
OPINION  OF  THE  ANCIENTS  that  it  is  not  impossible  to  con- 
vert one  element  into  another,  or  in  the  language  of  the 
Ancients,  to  make  gold.  Hence  we  have  placed  the  Chryso- 
poeia  of  Cleopatra  (Berthelot)  at  the  top  of  page  385  above 
our  old  system  of  valence.  Also  the  Ouroborus  on  the  first 
page  of  this  book  and  here  at  its  close. 

18.  The  element  atoms  are  different  compounds  from  those 
of  compound  atoms;  for  in  the  first  the  constituent  atoms  or 
pantogen  atoms  are  rigidly  united,  admitting  not  even  of 
separate  vibrations  (96,  11).  It  will  accordingly  require  AN 
IMMENSE  AMOUNT  OF  ENERGY  to  effect  their  decomposition. 
But  whether  that  is  soon  effected  or  not,  I think  it  is  now 
evident  that  all  matter  is  One  which  we  call  Pantogen, 
.and  that  the  Ancients  were  right  in  saying:  EN  TO  nAN. 


Hinrichs’ 

Contributions  to  Atom-Mechanics. 


PUBLISHED  IN  THE  COMPTES  RENDUS  OF  THE 
ACADEMY  OF  SCIENCES  OF  PARIS. 


FIRST  SERIES. 

GENERAL  MECHANICS  OF  THE  THREE  STATES  OF 
AGGREGATION. 

1873:  Tome  76,  p.  1357;  p.  1408;  p.  1592. 

1875:  Tome  80,  p.  47;  p.  565;  p.  766. 

SECOND  SERIES. 

THE  GENERAL  RELATIONS  BETWEEN  BOILING  POINT, 
PRESSURE  AND  ATOMIC  WEIGHT  AND 
FORM  OF  COMPOUNDS. 

1891:  Tome  112,  p.  998;  p.  1127;  p.  1436. 

1891:  Tome  113,  p.  36;  p.  313;  p.  468;  p.  500;  p.  743, 
p.  798. 

THIRD  SERIES. 

THE  GENERAL  MECHANICAL  EFFECTS  OF  CHEMICAL 
SUBSTITUTION. 

1892:  Tome  114;  p.  597;  p.  1015;  p.  1064;  p.  1113;  p. 
1272;  p.  1367. 

1892:  Tome  115,  p.  177;  p.  239;  p.  314. 

FOURTH  SERIES. 

DETERMINATION  OF  THE  TRUE  ATOMIC  WEIGHT  OF 
THE  ELEMENTS. 

1892:  Tome  115,  p.  1074. 

1893:  Tome  116,  p.  431;  p.  695;  p.  753. 

1893:  Tome  117,  p.  663;  p.  1075. 

1894:  Tome  118,  p.  528. 


A reference  list  to  the  author’s  contributions  to  Cosmical 
Science,  Meteorology  and  Technical  Chemistry  has  been  pub- 
lished elsewhere.  The  work  in  Meteorology  has  been  quite 
voluminous. 


HINRICHS’ 

SEPARATE  WORKS  ON  ATOM-MECHANICS. 

PROGRAMME  DER  ATOM-MECHANIK,  Oder,  die  Chemie  eine 
Mechanik  der  Pan-Atome. — 44  pp.  4®,  Iowa  City,  Iowa, 
1867.  French  Resume  of  same,  4 pp.  4®,  November 
1867.  English  Resume,  4 pp.  4^  August  1867. 

THE  PRINCIPLES  OF  PURE  CRYSTALLOGRAPHY.— pp.  IV, 
44,  in  8®,  Davenport,  1871.  See  especially.  Chapter  VI. 

THE  METHOD  OF  QUANTITATIVE  INDUCTION  IN  PHYSI- 
CAL SCIENCE.— Davenport,  1872.  See  especially  the 
last  section,  p.  36,  giving  the  Mechanics  of  the  three 
States  of  Aggregation. 

THE  PRINCIPLES  OF  CHEMISTRY  AND  MOLECULAR 
Mechanics. — 200  pp.,  8®,  with  two  plates.  Cloth. 
Davenport  and  New  York,  1874. 

BEITRAEGE  ZUR  DYNAMIK  DES  CHEMISCHEN  MOLE- 
KUELS. — Leipzig,  Gustav  Fock,  1892: 

I. — The  Molecule  as  a System  of  Material  Points.  II. — The  Energy 
of  the  Molecule.  III. — Graphical  Structural  Fprmulae.  IV. — The 
Moments  of  Inertia  of  the  Molecules.  VI. — The  Boiling  Points  of 
Isomeric  Bodies  Determined  by  the  Moment  of  Inertia  of  the 
Molecules. 

The  above  Beitraege  will  be  sent  by  the  undersigned  on  receipt 
of  50  cents. 

These  Beitraege  were  sent  to  A.  W.  Hofmann  for  the  Deutsche 
CiiEMiscHE  Gesellsehaft  (I,  II,  April,  1872;  III — VI,  April,  1873),  of 
which  the  author  was  a Foreign  Member. 

No  one  at  Berlin  did  understand  these  papers.  This  very  interesting 
and  characteristic  episode  in  the  history  of  Atom-Mechanics  is  con- 
tained in  the  above  edition  of  1892. 


THE  TRUE  ATOMIC  WEIGHTS  of  the  Chemical  Elements 
and  the  Unity  of  Matter.  With  Plates  and  Diagrams. 
St.  Louis:  Carl  Gustav  Hinrichs,  Publisher.  B.  Wester- 
mans  & Co.,  New  York.  1894.  XVI  and  256  pp.  8 vo. 
Will  be  sent  prepaid  to  any  part  of  the  Postal  Union  upon 
receipt  of  price  ($3.00)  by  the  publisher. 

Address  CARL  GUSTAV  HINRICHS,  Publisher, 

ST.  LOUIS,  MO.,  U.  S.  A. 


CLEOPATRA’S  CHRYSOPOEIA  (Berthelot). 


THE  STUDENTS  ATLAS, 

V.  Supplement. 


CHEMICAL  VALENCE,  HINRICHS,  1867. 


ATOMECHANIK,  P.  15. 


385 


38G 


WEIGHT  AND  MEASURE. 


887 


GASOMETRIC  APPARATUS, 


38S 


GAS  MANIPULATION. 


DISTILLING  AND  EXTRACTION  APPARATUS. 


PROFESSOR’S  STAND  IN  THE  CHEMICAL  LABORATORY, 
ST.  LOUIS  COLLEGE  OF  PHARMACY. 


889 


MICROGRAPHS  OF  FERMENTS. 

LECTURE  71. 


SACCHAROMYCES— 
-CEREVISI/£,  YOUNG. 

OLD. 


BACILLUS— 
-ACETICUS. 
-ACIDI  LACTICI. 


890 


HINRICHS.  THE  ELEMENTS.  1867. 

WALL  CHART. 


891 


THE  DODECAHEDRON. 


THE  PYRITOHEDRON 


HAUY,  ORIGIN  OF  SECONDARY  FORMS. 


392 


•/^ 


.398 


894 


BENZOL. 


395 


ATOMECHANIK,  P.  9. 


896 


o 


397 


A 

2 

£ 


U 

<!> 

Q> 

X 


ORIGIN  OF  THE  “ PERIODIC  LAW.” 


398 


HALF  OF  PAGE  34  FROM 

HINRICHS’  PROGRAMME  DER  ATOMECHANIK,  1867. 


399 


400 


A LOOK-OUT  TO  THE  OLD  PASTURES  (67,  I). 

Lunden  was  the  chief  town  of  North  Ditmarsia,  the  little  Republic  between  Eyder,  Elbe  and  North  Sea  that  maintained 
its  independence  for  centuries,  and  kept  itself  free  from  all  feudal  institutions. 


